{"gene":"ACADM","run_date":"2026-06-09T22:02:38","timeline":{"discoveries":[{"year":1991,"finding":"The prevalent 985A→G mutation in MCAD causes a lysine-to-glutamate substitution at position 304 (K304E, also referred to as K329E in mature protein numbering) that results in inactive enzyme due to impaired ability to form active tetramers, demonstrated by expression of mutant MCAD cDNA in E. coli producing inactive protein.","method":"E. coli expression of mutant MCAD cDNA, enzyme activity assay, immunoblot","journal":"Human genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro expression with activity measurement, replicated across multiple independent labs (PMID:1902818, PMID:1684086, PMID:1363805)","pmids":["1902818","1684086","1363805"],"is_preprint":false},{"year":1992,"finding":"Expression of K304E mutant MCAD in eukaryotic COS-7 cells showed that mutant protein is synthesized and transported into mitochondria in similar amounts to wild-type, achieves correct mature protein size, adopts tetrameric structure, but is present at consistently lower steady-state levels than wild-type and is degraded more readily, indicating post-import instability rather than import defect.","method":"EBV-based eukaryotic expression in COS-7 cells, immunoblot, enzyme activity assay, pulse-chase labeling","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (pulse-chase, activity assay, immunoblot) in eukaryotic expression system; consistent with bacterial expression data","pmids":["1382617"],"is_preprint":false},{"year":1993,"finding":"Co-overexpression of bacterial chaperonins GroEL/GroES partially rescues solubility and tetramer formation of K304E MCAD expressed in E. coli, but even soluble K304E tetramers show reduced amounts relative to wild-type, indicating the K304E mutation primarily impairs the rate of polypeptide folding and subunit assembly. Neutral substitution K304Q restores more activity than K304E, demonstrating that the negative charge of glutamate specifically impairs subunit docking.","method":"E. coli co-overexpression with GroEL/GroES, native PAGE, enzyme activity assay, Western blot","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with chaperonins plus mutagenesis (K304Q and K304E/D346K constructs), multiple orthogonal methods","pmids":["8104486"],"is_preprint":false},{"year":1993,"finding":"The R28C mutation (T157C in cDNA) in MCAD primarily affects polypeptide folding; based on the known 3D structure of MCAD, it is proposed to destroy a salt bridge between arginine-28 and glutamate-86. Expression in COS-7 cells confirmed impaired formation of enzymatically active protein.","method":"COS-7 cell expression of mutant MCAD cDNA, enzyme activity assay, structural inference from 3D structure","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — eukaryotic expression with activity measurement, structural inference but no direct mutagenesis of the proposed salt bridge","pmids":["8102510"],"is_preprint":false},{"year":1994,"finding":"In vitro import of MCAD into isolated rat liver mitochondria demonstrated that: (1) newly imported MCAD first forms a transient complex with mitochondrial hsp70 (hsp70mit), (2) is then transferred to hsp60 (a ~700 kDa high-molecular-weight complex), and (3) subsequently released as mature tetramer in an ATP-dependent manner. K304E MCAD binds hsp70mit and transfers to hsp60 normally, but the hsp60–K304E complex is abnormally stable and resistant to ATP-driven release, indicating the folding/release step from hsp60 is impaired.","method":"In vitro import into isolated mitochondria, gel filtration, specific antibody immunoprecipitation (anti-hsp60, anti-hsp70), ATP chase experiment","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro import assay with multiple fractionation and immunoprecipitation steps; directly identifies molecular chaperone interactions and ATP dependence","pmids":["7905878"],"is_preprint":false},{"year":1995,"finding":"The R28C and K304E mutations in MCAD have distinct molecular effects: R28C predominantly affects folding (amounts of active enzyme can be modulated from undetectable to 100% of wild-type by chaperonin co-overexpression and low growth temperature), while K304E affects both folding and oligomer assembly/stability (active enzyme cannot exceed ~50% of wild-type even under optimal chaperonin conditions), and K304E assembled tetramers show decreased thermal stability.","method":"E. coli expression with and without GroEL/GroES co-overexpression, enzyme activity assay, thermal stability assay, Western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with mutagenesis, temperature variation, and chaperonin titration; multiple artificially constructed mutants (K304Q, K304E/D346K) used as controls","pmids":["7730333"],"is_preprint":false},{"year":1994,"finding":"Two-dimensional gel electrophoresis of MCAD expressed in eukaryotic cells revealed two spots for mature MCAD with different isoelectric points, demonstrating that MCAD undergoes post-translational modification in mitochondria after transit peptide removal. The pI shift is compatible with phosphorylation of one aspartic acid residue per monomer. The modified form accumulates over time relative to the unmodified form, indicating the modification is time-dependent. The K304E mutant shows a higher ratio of unmodified form, suggesting the modification efficiency or stability of the modified form is impaired by K304E.","method":"2D gel electrophoresis, pulse labeling, expression in E. coli and COS-7 cells","journal":"Biochemical medicine and metabolic biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — 2D gel electrophoresis with pulse-chase in eukaryotic cells; pI shift is compatible with phosphorylation but not directly confirmed by phosphorylation assay","pmids":["7917465"],"is_preprint":false},{"year":1995,"finding":"The reductive half-reaction of MCAD with octanoyl-CoA as substrate generates two kinetically distinct forms of the reduced enzyme (MCAD-FADH2)–octenoyl-CoA charge-transfer complexes. Octenoyl-CoA dissociates from the more stable complex (CT2) via two pathways: a 'facile' pathway involving reversal of the reductive half-reaction (releasing octanoyl-CoA), and a 'restricted' pathway involving direct slow dissociation of octenoyl-CoA yielding MCAD-FADH2. The oxidase activity of MCAD is suppressed as long as reduced enzyme remains in charge-transfer complex form, emerging concomitantly with conversion of CT2 to the MCAD-FADH2–octenoyl-CoA Michaelis complex.","method":"Stopped-flow kinetics, in vitro enzymatic assay with O2 monitoring","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstituted kinetic analysis with defined substrates; multiple kinetic measurements establishing the charge-transfer complex mechanism","pmids":["7626613"],"is_preprint":false},{"year":2001,"finding":"The 199T→C mutation in MCAD (Y67H) is a mild folding mutation: overexpression experiments showed that it exhibits decreased levels of enzyme activity only under stringent conditions (i.e., impaired folding is partially compensated under permissive conditions), distinguishing it from the severe K304E mutation.","method":"Overexpression experiments in E. coli, enzyme activity assay under varying conditions","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — heterologous expression with activity measurement; single lab, functional characterization with defined conditions","pmids":["11349232"],"is_preprint":false},{"year":2005,"finding":"The R256T mutation in MCAD results in a well-folded, stable protein that is completely devoid of catalytic activity, identifying R256 as critical for catalysis rather than folding. The K364R mutation by contrast causes a folding defect (protein is only active when GroELS chaperonin is co-overexpressed and shows reduced thermostability). Neither mutant shows marked FAD depletion.","method":"E. coli overexpression with and without GroELS, enzyme activity assay, protein purification, thermostability assay, Western blot","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with purified proteins, chaperonin rescue experiments, and thermostability assays; clear mechanistic distinction between folding and catalytic mutations","pmids":["16128823"],"is_preprint":false},{"year":2007,"finding":"A missense mutation in MCAD exon 5 primarily causes disease by inactivating an exonic splicing enhancer (ESE), leading to exon skipping rather than by direct protein dysfunction. The ESE functions by antagonizing a juxtaposed exonic splicing silencer (ESS) to define a suboptimal 3′ splice site. A synonymous polymorphic variant in exon 5 inactivates the ESS and renders splicing immune to the deleterious ESE mutation, demonstrating context-dependent SNP effects on pre-mRNA splicing.","method":"Patient cell RNA analysis, minigene splicing assays, in vitro splicing assays","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (patient cells, minigenes, in vitro assays); identified specific ESE/ESS elements with functional validation","pmids":["17273963"],"is_preprint":false},{"year":2013,"finding":"A synonymous SNP c.1161A>G in ACADM exon 11 affects pre-mRNA splicing efficiency. The c.1161A allele is associated with exon 11 missplicing; the c.1161G allele corrects this missplicing, apparently by altering the relative binding of splicing regulatory proteins SRSF1 and hnRNP A1, resulting in higher levels of full-length MCAD protein from the G allele.","method":"Minigene splicing assays, RNA-seq analysis, splicing factor binding inference","journal":"Molecular genetics and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — minigene functional assay plus RNA-seq validation; splicing factor binding inferred rather than directly demonstrated by binding assay","pmids":["23810226"],"is_preprint":false},{"year":2018,"finding":"PINK1 kinase mediates phosphorylation of MCAD in vivo in Drosophila, identified by unbiased phosphoproteomic screen. Mimicking MCAD phosphorylation in a PINK1-null background rescued climbing, flight, thorax, and wing defects of PINK1 null flies, and partially corrected metabolic disruptions in acylcarnitines and amino acids, placing MCAD downstream of PINK1 in a pathway relevant to mitochondrial function and fatty acid metabolism.","method":"Unbiased phosphoproteomic screen in Drosophila, phosphomimetic transgene rescue, metabolic profiling (acylcarnitines and amino acids)","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphoproteomic identification plus in vivo genetic rescue with phosphomimetic; single lab, Drosophila model","pmids":["29563254"],"is_preprint":false},{"year":2021,"finding":"SREBP1 acts as a negative transcriptional regulator of ACADM in hepatocellular carcinoma. CAV1 (caveolin-1) was found to inhibit fatty acid oxidation by enhancing nuclear accumulation of SREBP1, which in turn suppresses ACADM expression and activity, promoting HCC cell aggressiveness. ACADM suppression led to elevated triglyceride, phospholipid, and lipid droplet levels and increased HCC cell motility.","method":"Loss-of-function and gain-of-function experiments, SREBP1 inhibitor treatment, in vivo xenograft model, lipid assays, cell motility assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional KD/OE with defined phenotypic readouts and in vivo validation; single lab but multiple assays","pmids":["33975883"],"is_preprint":false},{"year":2023,"finding":"MCAD (encoded by ACADM) participates in a host-microbe co-metabolic pathway for hippuric acid generation: gut bacteria reduce phenylalanine to phenylpropionic acid, and the host re-oxidizes phenylpropionic acid via MCAD (β-oxidation). This was demonstrated using MCAD-/- germ-free mice colonized with specific bacteria combined with stable isotope tracing and untargeted metabolomics, which also identified additional microbial metabolites processed by MCAD in host circulation.","method":"Stable isotope tracing, germ-free MCAD-/- mouse model, gnotobiotic colonization, untargeted metabolomics","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — genetic knockout combined with stable isotope tracing and metabolomics in gnotobiotic mouse model; multiple orthogonal approaches establish substrate and pathway","pmids":["36720857"],"is_preprint":false},{"year":2023,"finding":"ACADM interacts with the NSP4 protein of porcine epidemic diarrhea virus (PEDV), identified by immunoprecipitation-mass spectrometry. The interaction was confirmed by co-immunoprecipitation and laser confocal co-localization. ACADM overexpression inhibits PEDV replication while knockdown facilitates it. Mechanistically, ACADM reduces cellular free fatty acid levels and β-oxidation by hindering AMPK-mediated lipophagy, thereby suppressing PEDV replication.","method":"Immunoprecipitation-mass spectrometry, co-immunoprecipitation, laser confocal microscopy, overexpression/knockdown functional assays, viral replication assays, lipophagy assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus functional KD/OE with viral replication readout and AMPK pathway analysis; single lab","pmids":["39002673"],"is_preprint":false},{"year":2023,"finding":"Multiple MCAD missense variants alter FAD cofactor incorporation: half of studied variants showed FAD content <65% of wild-type. A correlation was established between FAD content and cofactor affinity, proteolytic stability, thermostability, and thermal inactivation rate. The p.Y372N variant assembles predominantly as dimers rather than tetramers. Some variants show altered substrate chain-length dependence and altered interaction with electron-transferring-flavoprotein (ETF). FAD supplementation structurally rescued some variants, suggesting mitochondrial FAD availability can modulate variant MCAD levels.","method":"Heterologous expression, FAD content measurement, enzyme kinetics with varied substrates, thermal stability assay, proteolytic stability assay, ETF interaction assay, native gel analysis","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal biochemical methods (FAD quantification, kinetics, thermostability, ETF binding, gel electrophoresis) on 12 variants in a single rigorous study","pmids":["37257730"],"is_preprint":false},{"year":2014,"finding":"Functional characterization of 18 ACADM missense variants by heterologous E. coli overexpression identified three variants (Y42H, E18K, R6H) with moderate impairment (22–47% residual octanoyl-CoA oxidation activity, normal temperature sensitivity, activity rescued to 100% by chaperonin co-overexpression), while 15 others showed severely reduced residual activities (<5%). Cross-linking experiments and 3D structure mapping were used to infer structural consequences.","method":"E. coli heterologous expression, enzyme activity assay with multiple substrates, GroEL/GroES co-overexpression, temperature variation assay, cross-linking experiments, 3D structure mapping","journal":"Journal of inherited metabolic disease","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with mutagenesis, multiple substrates, chaperonin rescue, and structural mapping for 18 variants in a single systematic study","pmids":["24966162"],"is_preprint":false},{"year":2004,"finding":"A novel splice mutation IVS3-1G>C in MCAD leads to deletion of 7 bp and introduction of a premature stop codon through complete missplicing of MCAD mRNA. The misspliced mRNA is reduced in abundance due to nonsense-mediated mRNA decay (NMD), resulting in total absence of functional MCAD enzyme. This was the first functionally characterized splice mutation in the MCAD gene.","method":"RT-PCR analysis of patient mRNA, sequence analysis, functional characterization of splice products","journal":"Molecular genetics and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct mRNA analysis from patient cells demonstrating complete missplicing and NMD; single lab, patient-based study","pmids":["15171999"],"is_preprint":false},{"year":2015,"finding":"A novel splice site mutation c.600-18G>A in ACADM activates a cryptic splice site that competes with the natural splice site, producing three transcripts, two of which result in truncated non-functional MCAD protein. Only partial missplicing occurs, leaving sufficient functional MCAD for a mild deficiency phenotype. The degree of missplicing was found to be temperature-sensitive, with octanoyl-CoA oxidation rate decreasing during febrile infection.","method":"RT-PCR and mRNA analysis in granulocytes and monocytes, enzyme activity measurement (octanoyl-CoA oxidation) before and during febrile infection","journal":"BMC medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct mRNA and enzyme activity analysis in patient cells; temperature sensitivity demonstrated by in vivo correlation; single case/family","pmids":["26223887"],"is_preprint":false},{"year":2008,"finding":"MCAD-deficient (MCAD-/-) mice show specific alterations in hepatic carbohydrate management under metabolic stress: during lipopolysaccharide-induced acute phase response, de novo glucose-6-phosphate synthesis was significantly decreased (-20%) and newly formed G6P was preferentially directed toward glycogen, leading to decreased hepatic glucose output. During fasting alone, de novo G6P synthesis was not affected, suggesting compensatory mechanisms exist under that condition.","method":"MCAD-/- knockout mice, quantitative flux measurements with stable isotopes, microarray gene expression analysis, metabolic challenge (fasting, LPS)","journal":"Hepatology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout model with quantitative metabolic flux measurements (stable isotope) under defined stress conditions; multiple independent readouts","pmids":["18459129"],"is_preprint":false},{"year":1995,"finding":"In vitro incubation of MCAD-deficient human fibroblasts with stable isotope-labeled fatty acid probes produced acylcarnitine profiles characteristic of MCAD deficiency regardless of the underlying DNA mutation: elevated octanoyl-, decanoyl-, and decenoylcarnitine with specific octanoylcarnitine-to-decanoylcarnitine ratios, indicating that MCAD-deficient cells readily convert decanoyl-CoA to octanoyl-CoA but cannot further oxidize octanoyl-CoA.","method":"Stable isotope-labeled fatty acid incubation with human fibroblasts, tandem mass spectrometry analysis of acylcarnitine intermediates","journal":"Biochemical and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ex vivo functional assay in patient-derived cells with isotope tracing; establishes substrate accumulation pattern independent of genotype","pmids":["7551818"],"is_preprint":false}],"current_model":"ACADM (MCAD) encodes a mitochondrial homotetrameric flavoenzyme that catalyzes the first step of β-oxidation for medium-chain (C4–C12) acyl-CoAs via an FAD-dependent mechanism generating a charge-transfer complex with the enoyl-CoA product; newly imported MCAD monomers are chaperoned sequentially by mitochondrial hsp70 and hsp60 in an ATP-dependent folding pathway before assembling into active tetramers, a process disrupted by the prevalent K304E/K329E disease mutation which impairs the hsp60 release step and subunit docking through charge repulsion; the enzyme also undergoes mitochondrial post-translational modification (likely phosphorylation) after transit peptide removal, is regulated transcriptionally by the CAV1/SREBP1 axis, and is phosphorylated downstream of PINK1 kinase, with loss of MCAD function causing accumulation of medium-chain acylcarnitines and fatty acids, impaired hepatic glucose homeostasis under metabolic stress, and disrupted host processing of microbiota-derived metabolites including hippurate."},"narrative":{"mechanistic_narrative":"ACADM encodes the mitochondrial flavoenzyme MCAD, which catalyzes the rate-determining first dehydrogenation step of medium-chain fatty acid β-oxidation; in MCAD-deficient cells decanoyl-CoA is readily shortened to octanoyl-CoA but octanoyl-CoA cannot be further oxidized, producing the characteristic accumulation of octanoyl-, decanoyl-, and decenoylcarnitine [PMID:7551818]. Catalysis proceeds through an FAD-dependent reductive half-reaction with octanoyl-CoA that generates kinetically distinct MCAD-FADH2–octenoyl-CoA charge-transfer complexes, and the enzyme's latent oxidase activity is suppressed while these charge-transfer species persist [PMID:7626613]; electrons are relayed to electron-transferring flavoprotein (ETF), and disease variants can alter both substrate chain-length dependence and ETF interaction [PMID:37257730]. Proper FAD incorporation is coupled to cofactor affinity, proteolytic and thermal stability, and correct tetramer assembly, with FAD supplementation able to structurally rescue some variants [PMID:37257730]. Newly imported MCAD monomers are folded along an ATP-dependent chaperone pathway in which they first bind mitochondrial hsp70 and are then transferred to hsp60 before release as mature tetramers [PMID:7905878]. The prevalent K304E (K329E) disease mutation does not impair import but introduces a charge that destabilizes the hsp60–MCAD complex against ATP-driven release and impairs subunit docking and tetramer stability; the neutral K304Q substitution restores far more activity, demonstrating that the glutamate negative charge is responsible [PMID:8104486, PMID:7905878, PMID:7730333]. Systematic variant studies separate folding/assembly defects, which are rescuable by chaperonin co-overexpression or permissive temperature, from purely catalytic lesions such as R256T that yield well-folded but inactive enzyme [PMID:16128823, PMID:24966162], and a large class of ACADM disease alleles act not on protein but on pre-mRNA splicing, disrupting exonic splicing enhancers/silencers or activating cryptic splice sites to cause exon skipping and NMD-mediated transcript loss [PMID:17273963, PMID:23810226, PMID:15171999]. Beyond classic β-oxidation, MCAD is transcriptionally repressed via the CAV1/SREBP1 axis in hepatocellular carcinoma [PMID:33975883], is phosphorylated downstream of PINK1 kinase in a pathway linking mitochondrial function to fatty acid metabolism [PMID:29563254], and re-oxidizes microbiota-derived phenylpropionic acid in a host-microbe co-metabolic pathway generating hippuric acid [PMID:36720857]. Loss of MCAD impairs hepatic glucose homeostasis under metabolic stress [PMID:18459129].","teleology":[{"year":1991,"claim":"Established the molecular basis of the most common ACADM disease allele by showing the 985A>G (K304E) substitution produces inactive enzyme through failure to form active tetramers, moving the field from genetic association to a defined protein defect.","evidence":"E. coli expression of mutant cDNA with activity assay and immunoblot, replicated across labs","pmids":["1902818","1684086","1363805"],"confidence":"High","gaps":["Did not resolve whether the defect was in synthesis, import, folding, or stability","No structural mechanism for why the charge change blocks assembly"]},{"year":1992,"claim":"Resolved that K304E is a post-import instability defect rather than an import defect, by showing mutant protein is imported, processed, and assembled into tetramers in eukaryotic cells but is degraded faster and present at lower steady-state levels.","evidence":"EBV-based expression in COS-7 cells with pulse-chase, activity assay, and immunoblot","pmids":["1382617"],"confidence":"High","gaps":["Did not identify the chaperone machinery handling the mutant","Did not localize the assembly step that fails"]},{"year":1994,"claim":"Defined the ordered ATP-dependent chaperone pathway for MCAD biogenesis (hsp70mit then hsp60 then tetramer release) and pinpointed the K304E lesion to an abnormally stable, ATP-resistant hsp60–MCAD intermediate, explaining the folding/assembly failure mechanistically.","evidence":"In vitro import into isolated rat liver mitochondria with gel filtration, anti-hsp60/anti-hsp70 immunoprecipitation, and ATP chase","pmids":["7905878"],"confidence":"High","gaps":["Did not establish whether the same release step limits other folding variants","No structural model of the hsp60–MCAD complex"]},{"year":1995,"claim":"Distinguished the contributions of folding versus oligomer assembly across mutations, showing R28C is a pure folding defect fully rescuable by chaperonins/temperature while K304E additionally impairs assembly and tetramer thermostability, and assigned the assembly defect specifically to glutamate's negative charge via the K304Q control.","evidence":"E. coli expression with GroEL/GroES titration, temperature variation, thermal stability assays, and engineered K304Q/K304E-D346K controls","pmids":["7730333","8104486"],"confidence":"High","gaps":["Did not quantify in vivo assembly kinetics in human mitochondria","Did not address cofactor loading during assembly"]},{"year":1995,"claim":"Defined the FAD-dependent catalytic mechanism, showing the reductive half-reaction with octanoyl-CoA forms kinetically distinct charge-transfer complexes that gate the enzyme's oxidase activity, providing the chemical basis of the dehydrogenase reaction.","evidence":"Stopped-flow kinetics with O2 monitoring on purified enzyme and defined substrate","pmids":["7626613"],"confidence":"High","gaps":["Did not connect charge-transfer kinetics to ETF electron transfer in physiologic context","Did not address chain-length selectivity at the kinetic level"]},{"year":1995,"claim":"Confirmed the metabolic block in patient cells by isotope tracing, showing MCAD-deficient fibroblasts convert decanoyl-CoA to octanoyl-CoA but cannot oxidize octanoyl-CoA, establishing the diagnostic acylcarnitine signature independent of genotype.","evidence":"Stable isotope-labeled fatty acid incubation of patient fibroblasts with tandem MS acylcarnitine profiling","pmids":["7551818"],"confidence":"Medium","gaps":["Ex vivo fibroblast model rather than in vivo flux","Did not quantify substrate chain-length boundaries precisely"]},{"year":2008,"claim":"Connected MCAD loss to systemic metabolism in vivo, showing MCAD-/- mice have impaired hepatic de novo glucose-6-phosphate synthesis and glucose output specifically under LPS-induced stress but not fasting alone, revealing condition-dependent metabolic vulnerability.","evidence":"MCAD-/- mice with stable-isotope flux measurements and microarray under fasting and LPS challenge","pmids":["18459129"],"confidence":"High","gaps":["Did not identify the compensatory mechanism active during fasting","Mouse stress paradigm may not map directly to human crisis physiology"]},{"year":2007,"claim":"Reframed a class of ACADM disease alleles as splicing rather than protein defects, showing an exon 5 missense mutation acts by inactivating an exonic splicing enhancer to cause exon skipping, with a synonymous SNP modulating the outcome.","evidence":"Patient cell RNA analysis, minigene and in vitro splicing assays identifying ESE/ESS elements","pmids":["17273963"],"confidence":"High","gaps":["Did not identify all trans-acting splicing factors involved","Generalizability to other exons not established here"]},{"year":2014,"claim":"Systematized genotype-to-function relationships across many variants, separating moderate chaperonin-rescuable folding variants from severe (<5% activity) lesions and mapping structural consequences, refining clinical interpretation.","evidence":"E. coli expression of 18 variants with multi-substrate activity assays, chaperonin rescue, temperature variation, cross-linking, and structure mapping","pmids":["24966162"],"confidence":"High","gaps":["Heterologous system may not capture human mitochondrial folding fully","Did not measure cofactor occupancy systematically"]},{"year":2005,"claim":"Dissociated catalysis from folding at the residue level, showing R256T yields a well-folded, stable but catalytically dead enzyme while K364R is a chaperonin-rescuable folding mutant, identifying R256 as catalytically essential.","evidence":"E. coli expression with GroELS rescue, purification, activity, and thermostability assays","pmids":["16128823"],"confidence":"High","gaps":["Did not define the precise catalytic role of R256 structurally","FAD depletion was not the explanation but cofactor coupling left open"]},{"year":2023,"claim":"Established FAD cofactor handling as a central determinant of variant stability and activity, correlating FAD content with affinity, proteolytic/thermal stability, assembly state, and ETF interaction, and showing FAD supplementation can structurally rescue some variants.","evidence":"Heterologous expression of 12 variants with FAD quantification, kinetics, thermostability, proteolysis, ETF binding, and native gels","pmids":["37257730"],"confidence":"High","gaps":["Therapeutic FAD/riboflavin benefit not tested in patients here","Mechanism of dimer-only assembly for p.Y372N not structurally resolved"]},{"year":2018,"claim":"Placed MCAD in a regulatory phosphorylation pathway, identifying it as a PINK1 substrate whose phosphomimetic form rescues PINK1-null phenotypes and metabolic defects, linking mitochondrial kinase signaling to fatty acid metabolism.","evidence":"Unbiased phosphoproteomics in Drosophila with phosphomimetic transgene rescue and metabolic profiling","pmids":["29563254"],"confidence":"Medium","gaps":["Drosophila model; human MCAD phosphosite and effect not demonstrated","Direct kinase-substrate biochemistry not shown"]},{"year":2021,"claim":"Identified transcriptional control of ACADM, showing the CAV1/SREBP1 axis represses ACADM to suppress fatty acid oxidation and promote hepatocellular carcinoma aggressiveness, extending MCAD biology into cancer metabolism.","evidence":"Loss/gain-of-function, SREBP1 inhibition, xenografts, lipid and motility assays","pmids":["33975883"],"confidence":"Medium","gaps":["Direct SREBP1 binding to the ACADM promoter not shown in this entry","Single tumor context"]},{"year":2023,"claim":"Revealed a host-microbe co-metabolic role, showing host MCAD re-oxidizes bacterially derived phenylpropionic acid to generate hippuric acid and processes additional microbial metabolites, broadening MCAD substrate scope beyond dietary fatty acids.","evidence":"Germ-free MCAD-/- mice with gnotobiotic colonization, stable isotope tracing, and untargeted metabolomics","pmids":["36720857"],"confidence":"High","gaps":["Full repertoire of microbial substrates not exhaustively defined","Physiologic significance of hippurate flux not quantified"]},{"year":2023,"claim":"Linked MCAD to antiviral lipid metabolism, showing it binds PEDV NSP4 and restricts viral replication by lowering free fatty acids and β-oxidation through suppression of AMPK-mediated lipophagy.","evidence":"IP-MS, reciprocal Co-IP, confocal colocalization, overexpression/knockdown viral replication and lipophagy assays","pmids":["39002673"],"confidence":"Medium","gaps":["Single lab; interaction interface not mapped","Relevance to human coronaviruses not established"]},{"year":null,"claim":"Whether MCAD phosphorylation (PINK1-dependent and the post-translational modification inferred from 2D-gel pI shifts) directly regulates enzyme activity, assembly, or turnover in human mitochondria remains undefined.","evidence":"No direct phosphorylation-function assay on human MCAD in the corpus","pmids":[],"confidence":"Low","gaps":["Phosphosite identity and stoichiometry in human cells unknown","Functional consequence of the 2D-gel-observed modification not directly tested","Link between PINK1 signaling and MCAD regulation in mammals unconfirmed"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[7,16,21]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[7]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[4,6]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[7,21,14]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[4]}],"complexes":[],"partners":["HSPD1","HSPA9","ETF","PINK1","SREBF1","CAV1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P11310","full_name":"Medium-chain specific acyl-CoA dehydrogenase, mitochondrial","aliases":["Medium chain acyl-CoA dehydrogenase","MCADH"],"length_aa":421,"mass_kda":46.6,"function":"Medium-chain specific acyl-CoA dehydrogenase is one of the acyl-CoA dehydrogenases that catalyze the first step of mitochondrial fatty acid beta-oxidation (FAO), breaking down fatty acids into acetyl-CoA and allowing the production of energy from fats (PubMed:1970566, PubMed:21237683, PubMed:2251268, PubMed:8823175). The first step of FAO consists in the proR-proR stereospecific alpha, beta-dehydrogenation of fatty acyl-CoA thioesters using the electron transfer flavoprotein (ETF) as their physiologic electron acceptor, resulting in the formation of trans-2-enoyl-CoA ((2E)-enoyl-CoA) (PubMed:2251268). ETF is the electron acceptor that transfers electrons to the main mitochondrial respiratory chain via ETF-ubiquinone oxidoreductase (ETF dehydrogenase) (PubMed:15159392, PubMed:25416781). Among the different mitochondrial acyl-CoA dehydrogenases, medium-chain specific acyl-CoA dehydrogenase has preference for fatty acyl-CoAs with saturated 6 to 12 carbons long primary chains, making it but can also catalyze longer chains such as C14 and C16 (PubMed:1970566, PubMed:21237683, PubMed:2251268, PubMed:8823175)","subcellular_location":"Mitochondrion matrix","url":"https://www.uniprot.org/uniprotkb/P11310/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ACADM","classification":"Not 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K364R, a folding mutation, and R256T, a catalytic-site mutation resulting in a well-folded but totally inactive protein.","date":"2005","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/16128823","citation_count":6,"is_preprint":false},{"pmid":"39682455","id":"PMC_39682455","title":"MiR-26a Inhibits Porcine Adipogenesis by Regulating ACADM and ACSL1 Genes and Cell Cycle Progression.","date":"2024","source":"Animals : an open access journal from MDPI","url":"https://pubmed.ncbi.nlm.nih.gov/39682455","citation_count":5,"is_preprint":false},{"pmid":"19055470","id":"PMC_19055470","title":"Mutation screening of the medium-chain acyl-CoA dehydrogenase (MCAD) and the ornithine transcarbamylase (OTC) genes by multiplex PCR amplification and sequencing.","date":"2009","source":"Clinical chemistry and laboratory medicine","url":"https://pubmed.ncbi.nlm.nih.gov/19055470","citation_count":5,"is_preprint":false},{"pmid":"11392180","id":"PMC_11392180","title":"Public health explores expanding newborn screening for cystic fibrosis, congenital adrenal hyperplasia, and medium-chain acyl coenzyme A dehydrogenase deficiency (MCAD).","date":"2001","source":"The Journal of the Oklahoma State Medical Association","url":"https://pubmed.ncbi.nlm.nih.gov/11392180","citation_count":5,"is_preprint":false},{"pmid":"29350094","id":"PMC_29350094","title":"Medium-chain acyl-CoA dehydrogenase deficiency: Two novel ACADM mutations identified in a retrospective screening.","date":"2018","source":"The Journal of international medical research","url":"https://pubmed.ncbi.nlm.nih.gov/29350094","citation_count":4,"is_preprint":false},{"pmid":"8590228","id":"PMC_8590228","title":"[Screening of A985 to G mutation of medium-chain acyl-CoA dehydrogenase (MCAD) gene in Normandy. Evaluation of the role of MCAD deficiency in sudden infant death].","date":"1995","source":"Comptes rendus des seances de la Societe de biologie et de ses filiales","url":"https://pubmed.ncbi.nlm.nih.gov/8590228","citation_count":4,"is_preprint":false},{"pmid":"26798524","id":"PMC_26798524","title":"Intermediate MCAD Deficiency Associated with a Novel Mutation of the ACADM Gene: c.1052C>T.","date":"2015","source":"Case reports in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26798524","citation_count":3,"is_preprint":false},{"pmid":"36292732","id":"PMC_36292732","title":"ACADM Frameshift Variant in Cavalier King Charles Spaniels with Medium-Chain Acyl-CoA Dehydrogenase Deficiency.","date":"2022","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/36292732","citation_count":3,"is_preprint":false},{"pmid":"37243123","id":"PMC_37243123","title":"Classical Swine Fever Virus Structural Glycoprotein E2 Interacts with Host Protein ACADM during the Virus Infectious Cycle.","date":"2023","source":"Viruses","url":"https://pubmed.ncbi.nlm.nih.gov/37243123","citation_count":3,"is_preprint":false},{"pmid":"9160189","id":"PMC_9160189","title":"Rapid testing for the MCAD G583A mutation, by PCR-mediated site directed mutagenesis, in an Australian population of SIDS patients.","date":"1997","source":"Disease markers","url":"https://pubmed.ncbi.nlm.nih.gov/9160189","citation_count":3,"is_preprint":false},{"pmid":"15559414","id":"PMC_15559414","title":"[Deficiency of the fatty-acid oxidising enzyme medium-chain acyl-CoA dehydrogenase (MCAD) in an adult, detected during a neonatal screening programme].","date":"2004","source":"Nederlands tijdschrift voor geneeskunde","url":"https://pubmed.ncbi.nlm.nih.gov/15559414","citation_count":3,"is_preprint":false},{"pmid":"40971725","id":"PMC_40971725","title":"NRF2-REGγ-ACADM/KLF15 Signaling Pathway Regulates the Browning of White Adipose Tissue to Modulate Obesity.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/40971725","citation_count":2,"is_preprint":false},{"pmid":"37257730","id":"PMC_37257730","title":"Functional and structural impact of 10 ACADM missense mutations on human medium chain acyl-Coa dehydrogenase.","date":"2023","source":"Biochimica et biophysica acta. Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/37257730","citation_count":2,"is_preprint":false},{"pmid":"1539377","id":"PMC_1539377","title":"[Medium chain acyl-CoA dehydrogenase (MCAD) deficiency: a life-threatening defect of fatty acid oxidation].","date":"1992","source":"Ugeskrift for laeger","url":"https://pubmed.ncbi.nlm.nih.gov/1539377","citation_count":2,"is_preprint":false},{"pmid":"10679947","id":"PMC_10679947","title":"Mutation 985A>G in the MCAD gene shows low incidence in Estonian population.","date":"2000","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/10679947","citation_count":2,"is_preprint":false},{"pmid":"22935320","id":"PMC_22935320","title":"Macro-AST: misleading finding in an adolescent with MCAD-deficiency.","date":"2012","source":"BMC gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/22935320","citation_count":2,"is_preprint":false},{"pmid":"10463467","id":"PMC_10463467","title":"Prevalence of the 985A>G mutation in the medium-chain acyl-CoA dehydrogenase (MCAD) gene in Sweden.","date":"1999","source":"Scandinavian journal of clinical and laboratory investigation","url":"https://pubmed.ncbi.nlm.nih.gov/10463467","citation_count":2,"is_preprint":false},{"pmid":"23546811","id":"PMC_23546811","title":"A Large Intragenic Deletion in the ACADM Gene Can Cause MCAD Deficiency but is not Detected on Routine Sequencing.","date":"2013","source":"JIMD reports","url":"https://pubmed.ncbi.nlm.nih.gov/23546811","citation_count":1,"is_preprint":false},{"pmid":"37368378","id":"PMC_37368378","title":"[Analysis of clinical characteristics and ACADM gene variants in four children with Medium chain acyl-CoA dehydrogenase deficiency].","date":"2023","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/37368378","citation_count":1,"is_preprint":false},{"pmid":"38114120","id":"PMC_38114120","title":"[Diosgenin alleviates NAFLD induced by a high-fat diet in rats via mTOR/SREBP-1c/HSP60/MCAD/SCAD signaling pathway].","date":"2023","source":"Zhongguo Zhong yao za zhi = Zhongguo zhongyao zazhi = China journal of Chinese materia medica","url":"https://pubmed.ncbi.nlm.nih.gov/38114120","citation_count":1,"is_preprint":false},{"pmid":"19551636","id":"PMC_19551636","title":"A985G mutation incidence in the medium-chain acyl-CoA dehydrogenase (MCAD) gene in Brazil.","date":"2009","source":"Genetics and molecular research : GMR","url":"https://pubmed.ncbi.nlm.nih.gov/19551636","citation_count":1,"is_preprint":false},{"pmid":"40619072","id":"PMC_40619072","title":"Transcriptomic and single-cell insights into mitochondrial genes NDUFA8, ECI2, and ACADM in acute myocardial infarction.","date":"2025","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/40619072","citation_count":0,"is_preprint":false},{"pmid":"40579130","id":"PMC_40579130","title":"[Down-regulation of ACADM-mediated lipotoxicity inhibits invasion and metastasis of estrogen receptor-positive breast cancer cells].","date":"2025","source":"Nan fang yi ke da xue xue bao = Journal of Southern Medical University","url":"https://pubmed.ncbi.nlm.nih.gov/40579130","citation_count":0,"is_preprint":false},{"pmid":"42247143","id":"PMC_42247143","title":"ACADM-mediated fatty acid β-oxidation pathway in atherosclerosis and abdominal aortic aneurysm.","date":"2026","source":"European heart journal","url":"https://pubmed.ncbi.nlm.nih.gov/42247143","citation_count":0,"is_preprint":false},{"pmid":"41767627","id":"PMC_41767627","title":"Exploring Deleterious Nonsynonymous SNPs in the ACADM Gene: Insights Into Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) via In Silico Analysis.","date":"2026","source":"Genetics research","url":"https://pubmed.ncbi.nlm.nih.gov/41767627","citation_count":0,"is_preprint":false},{"pmid":"3046055","id":"PMC_3046055","title":"[Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in 2 patients with symptoms of Reye syndrome].","date":"1988","source":"Tijdschrift voor kindergeneeskunde","url":"https://pubmed.ncbi.nlm.nih.gov/3046055","citation_count":0,"is_preprint":false},{"pmid":"41611076","id":"PMC_41611076","title":"Tachycardiomyopathy-like presentation in neonatal MCAD deficiency: A novel cardiac phenotype.","date":"2026","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41611076","citation_count":0,"is_preprint":false},{"pmid":"11400780","id":"PMC_11400780","title":"Screening of the most common medium-chain acyl CoA dehydrogenase (MCAD) deficiency mutation (K329E) in the Czech newborn population.","date":"1999","source":"The Southeast Asian journal of tropical medicine and public health","url":"https://pubmed.ncbi.nlm.nih.gov/11400780","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.22.25338591","title":"Mechanical Circulatory Assist Devices Stroke Subtype Classification: A Novel Stroke Classification System in Patients with Ventricular Assist Devices","date":"2025-10-27","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.22.25338591","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.19.25324093","title":"Clinical, biochemical and molecular characterization of newborns with fatty acid β-oxidation disorders: new variants in the<i>ACADM</i>,<i>ACADVL</i>and<i>SLC22A5</i>genes","date":"2025-03-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.19.25324093","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":52031,"output_tokens":6087,"usd":0.123699,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":15037,"output_tokens":5140,"usd":0.101843,"stage2_stop_reason":"end_turn"},"total_usd":0.225542,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1991,\n      \"finding\": \"The prevalent 985A→G mutation in MCAD causes a lysine-to-glutamate substitution at position 304 (K304E, also referred to as K329E in mature protein numbering) that results in inactive enzyme due to impaired ability to form active tetramers, demonstrated by expression of mutant MCAD cDNA in E. coli producing inactive protein.\",\n      \"method\": \"E. coli expression of mutant MCAD cDNA, enzyme activity assay, immunoblot\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro expression with activity measurement, replicated across multiple independent labs (PMID:1902818, PMID:1684086, PMID:1363805)\",\n      \"pmids\": [\"1902818\", \"1684086\", \"1363805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Expression of K304E mutant MCAD in eukaryotic COS-7 cells showed that mutant protein is synthesized and transported into mitochondria in similar amounts to wild-type, achieves correct mature protein size, adopts tetrameric structure, but is present at consistently lower steady-state levels than wild-type and is degraded more readily, indicating post-import instability rather than import defect.\",\n      \"method\": \"EBV-based eukaryotic expression in COS-7 cells, immunoblot, enzyme activity assay, pulse-chase labeling\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (pulse-chase, activity assay, immunoblot) in eukaryotic expression system; consistent with bacterial expression data\",\n      \"pmids\": [\"1382617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Co-overexpression of bacterial chaperonins GroEL/GroES partially rescues solubility and tetramer formation of K304E MCAD expressed in E. coli, but even soluble K304E tetramers show reduced amounts relative to wild-type, indicating the K304E mutation primarily impairs the rate of polypeptide folding and subunit assembly. Neutral substitution K304Q restores more activity than K304E, demonstrating that the negative charge of glutamate specifically impairs subunit docking.\",\n      \"method\": \"E. coli co-overexpression with GroEL/GroES, native PAGE, enzyme activity assay, Western blot\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with chaperonins plus mutagenesis (K304Q and K304E/D346K constructs), multiple orthogonal methods\",\n      \"pmids\": [\"8104486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"The R28C mutation (T157C in cDNA) in MCAD primarily affects polypeptide folding; based on the known 3D structure of MCAD, it is proposed to destroy a salt bridge between arginine-28 and glutamate-86. Expression in COS-7 cells confirmed impaired formation of enzymatically active protein.\",\n      \"method\": \"COS-7 cell expression of mutant MCAD cDNA, enzyme activity assay, structural inference from 3D structure\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — eukaryotic expression with activity measurement, structural inference but no direct mutagenesis of the proposed salt bridge\",\n      \"pmids\": [\"8102510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"In vitro import of MCAD into isolated rat liver mitochondria demonstrated that: (1) newly imported MCAD first forms a transient complex with mitochondrial hsp70 (hsp70mit), (2) is then transferred to hsp60 (a ~700 kDa high-molecular-weight complex), and (3) subsequently released as mature tetramer in an ATP-dependent manner. K304E MCAD binds hsp70mit and transfers to hsp60 normally, but the hsp60–K304E complex is abnormally stable and resistant to ATP-driven release, indicating the folding/release step from hsp60 is impaired.\",\n      \"method\": \"In vitro import into isolated mitochondria, gel filtration, specific antibody immunoprecipitation (anti-hsp60, anti-hsp70), ATP chase experiment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro import assay with multiple fractionation and immunoprecipitation steps; directly identifies molecular chaperone interactions and ATP dependence\",\n      \"pmids\": [\"7905878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The R28C and K304E mutations in MCAD have distinct molecular effects: R28C predominantly affects folding (amounts of active enzyme can be modulated from undetectable to 100% of wild-type by chaperonin co-overexpression and low growth temperature), while K304E affects both folding and oligomer assembly/stability (active enzyme cannot exceed ~50% of wild-type even under optimal chaperonin conditions), and K304E assembled tetramers show decreased thermal stability.\",\n      \"method\": \"E. coli expression with and without GroEL/GroES co-overexpression, enzyme activity assay, thermal stability assay, Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with mutagenesis, temperature variation, and chaperonin titration; multiple artificially constructed mutants (K304Q, K304E/D346K) used as controls\",\n      \"pmids\": [\"7730333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Two-dimensional gel electrophoresis of MCAD expressed in eukaryotic cells revealed two spots for mature MCAD with different isoelectric points, demonstrating that MCAD undergoes post-translational modification in mitochondria after transit peptide removal. The pI shift is compatible with phosphorylation of one aspartic acid residue per monomer. The modified form accumulates over time relative to the unmodified form, indicating the modification is time-dependent. The K304E mutant shows a higher ratio of unmodified form, suggesting the modification efficiency or stability of the modified form is impaired by K304E.\",\n      \"method\": \"2D gel electrophoresis, pulse labeling, expression in E. coli and COS-7 cells\",\n      \"journal\": \"Biochemical medicine and metabolic biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — 2D gel electrophoresis with pulse-chase in eukaryotic cells; pI shift is compatible with phosphorylation but not directly confirmed by phosphorylation assay\",\n      \"pmids\": [\"7917465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The reductive half-reaction of MCAD with octanoyl-CoA as substrate generates two kinetically distinct forms of the reduced enzyme (MCAD-FADH2)–octenoyl-CoA charge-transfer complexes. Octenoyl-CoA dissociates from the more stable complex (CT2) via two pathways: a 'facile' pathway involving reversal of the reductive half-reaction (releasing octanoyl-CoA), and a 'restricted' pathway involving direct slow dissociation of octenoyl-CoA yielding MCAD-FADH2. The oxidase activity of MCAD is suppressed as long as reduced enzyme remains in charge-transfer complex form, emerging concomitantly with conversion of CT2 to the MCAD-FADH2–octenoyl-CoA Michaelis complex.\",\n      \"method\": \"Stopped-flow kinetics, in vitro enzymatic assay with O2 monitoring\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstituted kinetic analysis with defined substrates; multiple kinetic measurements establishing the charge-transfer complex mechanism\",\n      \"pmids\": [\"7626613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The 199T→C mutation in MCAD (Y67H) is a mild folding mutation: overexpression experiments showed that it exhibits decreased levels of enzyme activity only under stringent conditions (i.e., impaired folding is partially compensated under permissive conditions), distinguishing it from the severe K304E mutation.\",\n      \"method\": \"Overexpression experiments in E. coli, enzyme activity assay under varying conditions\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — heterologous expression with activity measurement; single lab, functional characterization with defined conditions\",\n      \"pmids\": [\"11349232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The R256T mutation in MCAD results in a well-folded, stable protein that is completely devoid of catalytic activity, identifying R256 as critical for catalysis rather than folding. The K364R mutation by contrast causes a folding defect (protein is only active when GroELS chaperonin is co-overexpressed and shows reduced thermostability). Neither mutant shows marked FAD depletion.\",\n      \"method\": \"E. coli overexpression with and without GroELS, enzyme activity assay, protein purification, thermostability assay, Western blot\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with purified proteins, chaperonin rescue experiments, and thermostability assays; clear mechanistic distinction between folding and catalytic mutations\",\n      \"pmids\": [\"16128823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"A missense mutation in MCAD exon 5 primarily causes disease by inactivating an exonic splicing enhancer (ESE), leading to exon skipping rather than by direct protein dysfunction. The ESE functions by antagonizing a juxtaposed exonic splicing silencer (ESS) to define a suboptimal 3′ splice site. A synonymous polymorphic variant in exon 5 inactivates the ESS and renders splicing immune to the deleterious ESE mutation, demonstrating context-dependent SNP effects on pre-mRNA splicing.\",\n      \"method\": \"Patient cell RNA analysis, minigene splicing assays, in vitro splicing assays\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (patient cells, minigenes, in vitro assays); identified specific ESE/ESS elements with functional validation\",\n      \"pmids\": [\"17273963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A synonymous SNP c.1161A>G in ACADM exon 11 affects pre-mRNA splicing efficiency. The c.1161A allele is associated with exon 11 missplicing; the c.1161G allele corrects this missplicing, apparently by altering the relative binding of splicing regulatory proteins SRSF1 and hnRNP A1, resulting in higher levels of full-length MCAD protein from the G allele.\",\n      \"method\": \"Minigene splicing assays, RNA-seq analysis, splicing factor binding inference\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — minigene functional assay plus RNA-seq validation; splicing factor binding inferred rather than directly demonstrated by binding assay\",\n      \"pmids\": [\"23810226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PINK1 kinase mediates phosphorylation of MCAD in vivo in Drosophila, identified by unbiased phosphoproteomic screen. Mimicking MCAD phosphorylation in a PINK1-null background rescued climbing, flight, thorax, and wing defects of PINK1 null flies, and partially corrected metabolic disruptions in acylcarnitines and amino acids, placing MCAD downstream of PINK1 in a pathway relevant to mitochondrial function and fatty acid metabolism.\",\n      \"method\": \"Unbiased phosphoproteomic screen in Drosophila, phosphomimetic transgene rescue, metabolic profiling (acylcarnitines and amino acids)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphoproteomic identification plus in vivo genetic rescue with phosphomimetic; single lab, Drosophila model\",\n      \"pmids\": [\"29563254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SREBP1 acts as a negative transcriptional regulator of ACADM in hepatocellular carcinoma. CAV1 (caveolin-1) was found to inhibit fatty acid oxidation by enhancing nuclear accumulation of SREBP1, which in turn suppresses ACADM expression and activity, promoting HCC cell aggressiveness. ACADM suppression led to elevated triglyceride, phospholipid, and lipid droplet levels and increased HCC cell motility.\",\n      \"method\": \"Loss-of-function and gain-of-function experiments, SREBP1 inhibitor treatment, in vivo xenograft model, lipid assays, cell motility assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional KD/OE with defined phenotypic readouts and in vivo validation; single lab but multiple assays\",\n      \"pmids\": [\"33975883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MCAD (encoded by ACADM) participates in a host-microbe co-metabolic pathway for hippuric acid generation: gut bacteria reduce phenylalanine to phenylpropionic acid, and the host re-oxidizes phenylpropionic acid via MCAD (β-oxidation). This was demonstrated using MCAD-/- germ-free mice colonized with specific bacteria combined with stable isotope tracing and untargeted metabolomics, which also identified additional microbial metabolites processed by MCAD in host circulation.\",\n      \"method\": \"Stable isotope tracing, germ-free MCAD-/- mouse model, gnotobiotic colonization, untargeted metabolomics\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genetic knockout combined with stable isotope tracing and metabolomics in gnotobiotic mouse model; multiple orthogonal approaches establish substrate and pathway\",\n      \"pmids\": [\"36720857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ACADM interacts with the NSP4 protein of porcine epidemic diarrhea virus (PEDV), identified by immunoprecipitation-mass spectrometry. The interaction was confirmed by co-immunoprecipitation and laser confocal co-localization. ACADM overexpression inhibits PEDV replication while knockdown facilitates it. Mechanistically, ACADM reduces cellular free fatty acid levels and β-oxidation by hindering AMPK-mediated lipophagy, thereby suppressing PEDV replication.\",\n      \"method\": \"Immunoprecipitation-mass spectrometry, co-immunoprecipitation, laser confocal microscopy, overexpression/knockdown functional assays, viral replication assays, lipophagy assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus functional KD/OE with viral replication readout and AMPK pathway analysis; single lab\",\n      \"pmids\": [\"39002673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Multiple MCAD missense variants alter FAD cofactor incorporation: half of studied variants showed FAD content <65% of wild-type. A correlation was established between FAD content and cofactor affinity, proteolytic stability, thermostability, and thermal inactivation rate. The p.Y372N variant assembles predominantly as dimers rather than tetramers. Some variants show altered substrate chain-length dependence and altered interaction with electron-transferring-flavoprotein (ETF). FAD supplementation structurally rescued some variants, suggesting mitochondrial FAD availability can modulate variant MCAD levels.\",\n      \"method\": \"Heterologous expression, FAD content measurement, enzyme kinetics with varied substrates, thermal stability assay, proteolytic stability assay, ETF interaction assay, native gel analysis\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal biochemical methods (FAD quantification, kinetics, thermostability, ETF binding, gel electrophoresis) on 12 variants in a single rigorous study\",\n      \"pmids\": [\"37257730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Functional characterization of 18 ACADM missense variants by heterologous E. coli overexpression identified three variants (Y42H, E18K, R6H) with moderate impairment (22–47% residual octanoyl-CoA oxidation activity, normal temperature sensitivity, activity rescued to 100% by chaperonin co-overexpression), while 15 others showed severely reduced residual activities (<5%). Cross-linking experiments and 3D structure mapping were used to infer structural consequences.\",\n      \"method\": \"E. coli heterologous expression, enzyme activity assay with multiple substrates, GroEL/GroES co-overexpression, temperature variation assay, cross-linking experiments, 3D structure mapping\",\n      \"journal\": \"Journal of inherited metabolic disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with mutagenesis, multiple substrates, chaperonin rescue, and structural mapping for 18 variants in a single systematic study\",\n      \"pmids\": [\"24966162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"A novel splice mutation IVS3-1G>C in MCAD leads to deletion of 7 bp and introduction of a premature stop codon through complete missplicing of MCAD mRNA. The misspliced mRNA is reduced in abundance due to nonsense-mediated mRNA decay (NMD), resulting in total absence of functional MCAD enzyme. This was the first functionally characterized splice mutation in the MCAD gene.\",\n      \"method\": \"RT-PCR analysis of patient mRNA, sequence analysis, functional characterization of splice products\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct mRNA analysis from patient cells demonstrating complete missplicing and NMD; single lab, patient-based study\",\n      \"pmids\": [\"15171999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A novel splice site mutation c.600-18G>A in ACADM activates a cryptic splice site that competes with the natural splice site, producing three transcripts, two of which result in truncated non-functional MCAD protein. Only partial missplicing occurs, leaving sufficient functional MCAD for a mild deficiency phenotype. The degree of missplicing was found to be temperature-sensitive, with octanoyl-CoA oxidation rate decreasing during febrile infection.\",\n      \"method\": \"RT-PCR and mRNA analysis in granulocytes and monocytes, enzyme activity measurement (octanoyl-CoA oxidation) before and during febrile infection\",\n      \"journal\": \"BMC medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct mRNA and enzyme activity analysis in patient cells; temperature sensitivity demonstrated by in vivo correlation; single case/family\",\n      \"pmids\": [\"26223887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MCAD-deficient (MCAD-/-) mice show specific alterations in hepatic carbohydrate management under metabolic stress: during lipopolysaccharide-induced acute phase response, de novo glucose-6-phosphate synthesis was significantly decreased (-20%) and newly formed G6P was preferentially directed toward glycogen, leading to decreased hepatic glucose output. During fasting alone, de novo G6P synthesis was not affected, suggesting compensatory mechanisms exist under that condition.\",\n      \"method\": \"MCAD-/- knockout mice, quantitative flux measurements with stable isotopes, microarray gene expression analysis, metabolic challenge (fasting, LPS)\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout model with quantitative metabolic flux measurements (stable isotope) under defined stress conditions; multiple independent readouts\",\n      \"pmids\": [\"18459129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"In vitro incubation of MCAD-deficient human fibroblasts with stable isotope-labeled fatty acid probes produced acylcarnitine profiles characteristic of MCAD deficiency regardless of the underlying DNA mutation: elevated octanoyl-, decanoyl-, and decenoylcarnitine with specific octanoylcarnitine-to-decanoylcarnitine ratios, indicating that MCAD-deficient cells readily convert decanoyl-CoA to octanoyl-CoA but cannot further oxidize octanoyl-CoA.\",\n      \"method\": \"Stable isotope-labeled fatty acid incubation with human fibroblasts, tandem mass spectrometry analysis of acylcarnitine intermediates\",\n      \"journal\": \"Biochemical and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ex vivo functional assay in patient-derived cells with isotope tracing; establishes substrate accumulation pattern independent of genotype\",\n      \"pmids\": [\"7551818\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ACADM (MCAD) encodes a mitochondrial homotetrameric flavoenzyme that catalyzes the first step of β-oxidation for medium-chain (C4–C12) acyl-CoAs via an FAD-dependent mechanism generating a charge-transfer complex with the enoyl-CoA product; newly imported MCAD monomers are chaperoned sequentially by mitochondrial hsp70 and hsp60 in an ATP-dependent folding pathway before assembling into active tetramers, a process disrupted by the prevalent K304E/K329E disease mutation which impairs the hsp60 release step and subunit docking through charge repulsion; the enzyme also undergoes mitochondrial post-translational modification (likely phosphorylation) after transit peptide removal, is regulated transcriptionally by the CAV1/SREBP1 axis, and is phosphorylated downstream of PINK1 kinase, with loss of MCAD function causing accumulation of medium-chain acylcarnitines and fatty acids, impaired hepatic glucose homeostasis under metabolic stress, and disrupted host processing of microbiota-derived metabolites including hippurate.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ACADM encodes the mitochondrial flavoenzyme MCAD, which catalyzes the rate-determining first dehydrogenation step of medium-chain fatty acid β-oxidation; in MCAD-deficient cells decanoyl-CoA is readily shortened to octanoyl-CoA but octanoyl-CoA cannot be further oxidized, producing the characteristic accumulation of octanoyl-, decanoyl-, and decenoylcarnitine [#21]. Catalysis proceeds through an FAD-dependent reductive half-reaction with octanoyl-CoA that generates kinetically distinct MCAD-FADH2–octenoyl-CoA charge-transfer complexes, and the enzyme's latent oxidase activity is suppressed while these charge-transfer species persist [#7]; electrons are relayed to electron-transferring flavoprotein (ETF), and disease variants can alter both substrate chain-length dependence and ETF interaction [#16]. Proper FAD incorporation is coupled to cofactor affinity, proteolytic and thermal stability, and correct tetramer assembly, with FAD supplementation able to structurally rescue some variants [#16]. Newly imported MCAD monomers are folded along an ATP-dependent chaperone pathway in which they first bind mitochondrial hsp70 and are then transferred to hsp60 before release as mature tetramers [#4]. The prevalent K304E (K329E) disease mutation does not impair import but introduces a charge that destabilizes the hsp60–MCAD complex against ATP-driven release and impairs subunit docking and tetramer stability; the neutral K304Q substitution restores far more activity, demonstrating that the glutamate negative charge is responsible [#2, #4, #5]. Systematic variant studies separate folding/assembly defects, which are rescuable by chaperonin co-overexpression or permissive temperature, from purely catalytic lesions such as R256T that yield well-folded but inactive enzyme [#9, #17], and a large class of ACADM disease alleles act not on protein but on pre-mRNA splicing, disrupting exonic splicing enhancers/silencers or activating cryptic splice sites to cause exon skipping and NMD-mediated transcript loss [#10, #11, #18]. Beyond classic β-oxidation, MCAD is transcriptionally repressed via the CAV1/SREBP1 axis in hepatocellular carcinoma [#13], is phosphorylated downstream of PINK1 kinase in a pathway linking mitochondrial function to fatty acid metabolism [#12], and re-oxidizes microbiota-derived phenylpropionic acid in a host-microbe co-metabolic pathway generating hippuric acid [#14]. Loss of MCAD impairs hepatic glucose homeostasis under metabolic stress [#20].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Established the molecular basis of the most common ACADM disease allele by showing the 985A>G (K304E) substitution produces inactive enzyme through failure to form active tetramers, moving the field from genetic association to a defined protein defect.\",\n      \"evidence\": \"E. coli expression of mutant cDNA with activity assay and immunoblot, replicated across labs\",\n      \"pmids\": [\"1902818\", \"1684086\", \"1363805\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether the defect was in synthesis, import, folding, or stability\", \"No structural mechanism for why the charge change blocks assembly\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Resolved that K304E is a post-import instability defect rather than an import defect, by showing mutant protein is imported, processed, and assembled into tetramers in eukaryotic cells but is degraded faster and present at lower steady-state levels.\",\n      \"evidence\": \"EBV-based expression in COS-7 cells with pulse-chase, activity assay, and immunoblot\",\n      \"pmids\": [\"1382617\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the chaperone machinery handling the mutant\", \"Did not localize the assembly step that fails\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Defined the ordered ATP-dependent chaperone pathway for MCAD biogenesis (hsp70mit then hsp60 then tetramer release) and pinpointed the K304E lesion to an abnormally stable, ATP-resistant hsp60–MCAD intermediate, explaining the folding/assembly failure mechanistically.\",\n      \"evidence\": \"In vitro import into isolated rat liver mitochondria with gel filtration, anti-hsp60/anti-hsp70 immunoprecipitation, and ATP chase\",\n      \"pmids\": [\"7905878\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish whether the same release step limits other folding variants\", \"No structural model of the hsp60–MCAD complex\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Distinguished the contributions of folding versus oligomer assembly across mutations, showing R28C is a pure folding defect fully rescuable by chaperonins/temperature while K304E additionally impairs assembly and tetramer thermostability, and assigned the assembly defect specifically to glutamate's negative charge via the K304Q control.\",\n      \"evidence\": \"E. coli expression with GroEL/GroES titration, temperature variation, thermal stability assays, and engineered K304Q/K304E-D346K controls\",\n      \"pmids\": [\"7730333\", \"8104486\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not quantify in vivo assembly kinetics in human mitochondria\", \"Did not address cofactor loading during assembly\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defined the FAD-dependent catalytic mechanism, showing the reductive half-reaction with octanoyl-CoA forms kinetically distinct charge-transfer complexes that gate the enzyme's oxidase activity, providing the chemical basis of the dehydrogenase reaction.\",\n      \"evidence\": \"Stopped-flow kinetics with O2 monitoring on purified enzyme and defined substrate\",\n      \"pmids\": [\"7626613\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not connect charge-transfer kinetics to ETF electron transfer in physiologic context\", \"Did not address chain-length selectivity at the kinetic level\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Confirmed the metabolic block in patient cells by isotope tracing, showing MCAD-deficient fibroblasts convert decanoyl-CoA to octanoyl-CoA but cannot oxidize octanoyl-CoA, establishing the diagnostic acylcarnitine signature independent of genotype.\",\n      \"evidence\": \"Stable isotope-labeled fatty acid incubation of patient fibroblasts with tandem MS acylcarnitine profiling\",\n      \"pmids\": [\"7551818\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ex vivo fibroblast model rather than in vivo flux\", \"Did not quantify substrate chain-length boundaries precisely\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected MCAD loss to systemic metabolism in vivo, showing MCAD-/- mice have impaired hepatic de novo glucose-6-phosphate synthesis and glucose output specifically under LPS-induced stress but not fasting alone, revealing condition-dependent metabolic vulnerability.\",\n      \"evidence\": \"MCAD-/- mice with stable-isotope flux measurements and microarray under fasting and LPS challenge\",\n      \"pmids\": [\"18459129\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the compensatory mechanism active during fasting\", \"Mouse stress paradigm may not map directly to human crisis physiology\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Reframed a class of ACADM disease alleles as splicing rather than protein defects, showing an exon 5 missense mutation acts by inactivating an exonic splicing enhancer to cause exon skipping, with a synonymous SNP modulating the outcome.\",\n      \"evidence\": \"Patient cell RNA analysis, minigene and in vitro splicing assays identifying ESE/ESS elements\",\n      \"pmids\": [\"17273963\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify all trans-acting splicing factors involved\", \"Generalizability to other exons not established here\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Systematized genotype-to-function relationships across many variants, separating moderate chaperonin-rescuable folding variants from severe (<5% activity) lesions and mapping structural consequences, refining clinical interpretation.\",\n      \"evidence\": \"E. coli expression of 18 variants with multi-substrate activity assays, chaperonin rescue, temperature variation, cross-linking, and structure mapping\",\n      \"pmids\": [\"24966162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Heterologous system may not capture human mitochondrial folding fully\", \"Did not measure cofactor occupancy systematically\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Dissociated catalysis from folding at the residue level, showing R256T yields a well-folded, stable but catalytically dead enzyme while K364R is a chaperonin-rescuable folding mutant, identifying R256 as catalytically essential.\",\n      \"evidence\": \"E. coli expression with GroELS rescue, purification, activity, and thermostability assays\",\n      \"pmids\": [\"16128823\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the precise catalytic role of R256 structurally\", \"FAD depletion was not the explanation but cofactor coupling left open\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established FAD cofactor handling as a central determinant of variant stability and activity, correlating FAD content with affinity, proteolytic/thermal stability, assembly state, and ETF interaction, and showing FAD supplementation can structurally rescue some variants.\",\n      \"evidence\": \"Heterologous expression of 12 variants with FAD quantification, kinetics, thermostability, proteolysis, ETF binding, and native gels\",\n      \"pmids\": [\"37257730\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Therapeutic FAD/riboflavin benefit not tested in patients here\", \"Mechanism of dimer-only assembly for p.Y372N not structurally resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Placed MCAD in a regulatory phosphorylation pathway, identifying it as a PINK1 substrate whose phosphomimetic form rescues PINK1-null phenotypes and metabolic defects, linking mitochondrial kinase signaling to fatty acid metabolism.\",\n      \"evidence\": \"Unbiased phosphoproteomics in Drosophila with phosphomimetic transgene rescue and metabolic profiling\",\n      \"pmids\": [\"29563254\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Drosophila model; human MCAD phosphosite and effect not demonstrated\", \"Direct kinase-substrate biochemistry not shown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified transcriptional control of ACADM, showing the CAV1/SREBP1 axis represses ACADM to suppress fatty acid oxidation and promote hepatocellular carcinoma aggressiveness, extending MCAD biology into cancer metabolism.\",\n      \"evidence\": \"Loss/gain-of-function, SREBP1 inhibition, xenografts, lipid and motility assays\",\n      \"pmids\": [\"33975883\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct SREBP1 binding to the ACADM promoter not shown in this entry\", \"Single tumor context\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a host-microbe co-metabolic role, showing host MCAD re-oxidizes bacterially derived phenylpropionic acid to generate hippuric acid and processes additional microbial metabolites, broadening MCAD substrate scope beyond dietary fatty acids.\",\n      \"evidence\": \"Germ-free MCAD-/- mice with gnotobiotic colonization, stable isotope tracing, and untargeted metabolomics\",\n      \"pmids\": [\"36720857\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full repertoire of microbial substrates not exhaustively defined\", \"Physiologic significance of hippurate flux not quantified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linked MCAD to antiviral lipid metabolism, showing it binds PEDV NSP4 and restricts viral replication by lowering free fatty acids and β-oxidation through suppression of AMPK-mediated lipophagy.\",\n      \"evidence\": \"IP-MS, reciprocal Co-IP, confocal colocalization, overexpression/knockdown viral replication and lipophagy assays\",\n      \"pmids\": [\"39002673\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; interaction interface not mapped\", \"Relevance to human coronaviruses not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether MCAD phosphorylation (PINK1-dependent and the post-translational modification inferred from 2D-gel pI shifts) directly regulates enzyme activity, assembly, or turnover in human mitochondria remains undefined.\",\n      \"evidence\": \"No direct phosphorylation-function assay on human MCAD in the corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Phosphosite identity and stoichiometry in human cells unknown\", \"Functional consequence of the 2D-gel-observed modification not directly tested\", \"Link between PINK1 signaling and MCAD regulation in mammals unconfirmed\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [7, 16, 21]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [4, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [7, 21, 14]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"HSPD1\", \"HSPA9\", \"ETF\", \"PINK1\", \"SREBF1\", \"CAV1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}