{"gene":"TYSND1","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2007,"finding":"Tysnd1 is a peroxisomal protease responsible for both the removal of the N-terminal PTS2 leader peptide from PTS2-containing proteins (e.g., prethiolase Acaa1) and the specific limited cleavage of PTS1-containing peroxisomal beta-oxidation enzymes (e.g., Acox1, Hsd17b4, ScpX). Tysnd1 itself undergoes autocatalytic processing through removal of a presumably inhibitory N-terminal fragment, and its expression is induced by the PPARα agonist bezafibrate.","method":"Biochemical characterization of a previously uncharacterized protein; in vitro protease assays; identification of substrates; expression induction assay with bezafibrate","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct enzymatic assays identifying substrates and autocatalytic processing, replicated in subsequent independent studies","pmids":["17255948"],"is_preprint":false},{"year":2007,"finding":"Tysnd1-mediated proteolytic processing of peroxisomal beta-oxidation enzymes was proposed to promote their assembly into a supramolecular complex to enhance the rate of beta-oxidation.","method":"Biochemical characterization and substrate identification; model proposed based on experimental data","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — model supported by substrate identification and processing assays in a single lab, but supramolecular complex assembly not directly reconstituted","pmids":["17255948"],"is_preprint":false},{"year":2011,"finding":"Tysnd1 knockdown, but not PsLon (peroxisomal Lon protease) knockdown, results in accumulation of endogenous beta-oxidation enzymes in their premature (unprocessed) form, establishing Tysnd1 as the key processing protease. The proteolytic activity of oligomeric Tysnd1 is regulated by intermolecular self-cleavage converting the 60-kDa form into 15- and 45-kDa chains, which are then preferentially degraded by PsLon. Peroxisomal beta-oxidation of very long-chain fatty acids was significantly decreased by Tysnd1 knockdown and partially lowered by PsLon knockdown.","method":"siRNA knockdown of Tysnd1 and PsLon; Western blot for substrate processing; fatty acid beta-oxidation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal knockdown experiments with defined phenotypic readouts, multiple orthogonal methods (Western blot, functional beta-oxidation assay), single lab","pmids":["22002062"],"is_preprint":false},{"year":2011,"finding":"Tysnd1 is a serine protease-like domain-containing peroxisomal matrix protein that harbors a PTS1 targeting sequence, localizing it to the peroxisomal matrix.","method":"Sequence analysis and biochemical fractionation/localization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization established by fractionation and domain analysis, consistent across multiple studies","pmids":["22002062","17255948"],"is_preprint":false},{"year":2013,"finding":"In vivo, Tysnd1 is a peroxisomal cysteine endopeptidase that directly processes PTS2-containing prethiolase Acaa1, and PTS1-containing Acox1, Hsd17b4, and ScpX. Novel substrates Phyh and Agps (PTS2-containing proteins) were identified. Loss of Tysnd1 interferes with the peroxisomal localization of Acaa1, Phyh, and Agps, causing lipid metabolic abnormalities (altered plasmalogen composition), male infertility due to acrosomal cap defects in spermatozoa, and liver dysfunction upon phytol administration resembling mild Zellweger syndrome spectrum.","method":"Tysnd1 knockout (Tysnd1−/−) mouse model; analysis of substrate processing by Western blot; peroxisomal localization assays; lipidomics; histology","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with multiple orthogonal phenotypic and biochemical readouts, in vivo validation of enzymatic substrates and localization dependency","pmids":["23459139"],"is_preprint":false},{"year":2018,"finding":"Tysnd1 participates in a protein interaction network regulating peroxisomal fatty acid beta-oxidation, as revealed by immunoprecipitation-mass spectrometry analysis of Tysnd1 binding partners in mammalian cells.","method":"Co-immunoprecipitation combined with mass spectrometry (IP-MS)","journal":"Sub-cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single IP-MS experiment; no reciprocal validation or functional follow-up described in the abstract","pmids":["30378028"],"is_preprint":false},{"year":2023,"finding":"LONP2 (PsLon) depletion causes accumulation of its substrate TYSND1 protease in peroxisomes, consistent with LONP2 acting as the degrader of Tysnd1 cleavage products. Despite TYSND1 accumulation, TYSND1-dependent ACOX1 processing appeared normal at early stages of peroxisomal proteotoxic stress, indicating the regulatory relationship between LONP2 and TYSND1 in peroxisomal protein quality control.","method":"siRNA knockdown of LONP2; Western blot for TYSND1 and ACOX1 processing; peroxisomal phenotype analysis","journal":"Biology direct","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with direct measurement of substrate (TYSND1) accumulation and downstream processing, consistent with prior mechanistic model","pmids":["37736739"],"is_preprint":false}],"current_model":"TYSND1 is a peroxisomal matrix cysteine/serine endopeptidase (localized via a PTS1 signal) that processes both PTS1-containing beta-oxidation enzymes (Acox1, Hsd17b4, ScpX) and cleaves the N-terminal PTS2 targeting sequences from PTS2 precursor proteins (Acaa1, Phyh, Agps); this processing is required for correct peroxisomal localization and activity of substrate enzymes, thereby regulating peroxisomal fatty acid beta-oxidation. TYSND1 activity is itself regulated by intermolecular autocatalytic self-cleavage (converting the active 60-kDa form to inactive 15- and 45-kDa chains), with the cleavage products subsequently degraded by the peroxisomal Lon protease LONP2/PsLon, forming a proteolytic regulatory cascade."},"narrative":{"mechanistic_narrative":"TYSND1 is a peroxisomal matrix endopeptidase that processes the enzymes of the fatty acid beta-oxidation pathway and thereby governs their correct localization and activity [PMID:17255948, PMID:23459139]. Targeted to the peroxisomal matrix by a PTS1 signal, it performs two distinct proteolytic functions: it removes the N-terminal PTS2 leader peptide from PTS2-containing precursors (Acaa1/prethiolase, and the substrates Phyh and Agps) and carries out specific limited cleavage of PTS1-containing beta-oxidation enzymes (Acox1, Hsd17b4, ScpX) [PMID:17255948, PMID:23459139]. This processing is required for the proper peroxisomal localization of substrates such as Acaa1, Phyh, and Agps, and its activity sustains beta-oxidation of very long-chain fatty acids [PMID:22002062, PMID:23459139]. Genetic loss of Tysnd1 in mice produces unprocessed substrate accumulation, altered plasmalogen composition, male infertility from acrosomal cap defects, and phytol-induced liver dysfunction resembling the mild Zellweger syndrome spectrum [PMID:23459139]. TYSND1 is itself regulated by intermolecular autocatalytic self-cleavage that converts the active 60-kDa form into inactive 15- and 45-kDa chains, which are then degraded by the peroxisomal Lon protease LONP2/PsLon, establishing a proteolytic regulatory cascade for peroxisomal protein quality control [PMID:22002062, PMID:37736739]. Its expression is induced by the PPARalpha agonist bezafibrate [PMID:17255948].","teleology":[{"year":2007,"claim":"Established TYSND1 as a peroxisomal protease performing the dual reactions needed to mature beta-oxidation enzymes, answering how PTS2 leaders are removed and PTS1 enzymes are limited-cleaved within the peroxisome.","evidence":"Biochemical characterization with in vitro protease assays and substrate identification, plus bezafibrate induction assay","pmids":["17255948"],"confidence":"High","gaps":["Catalytic class (cysteine vs serine) not definitively resolved at this stage","In vivo physiological relevance not yet tested","Functional consequence of autocatalytic processing not quantified"]},{"year":2007,"claim":"Proposed that TYSND1-mediated processing promotes assembly of beta-oxidation enzymes into a supramolecular complex to accelerate the pathway, framing processing as functional rather than merely targeting-related.","evidence":"Model proposed from substrate identification and processing assays","pmids":["17255948"],"confidence":"Medium","gaps":["Supramolecular complex assembly not directly reconstituted","No structural evidence for the proposed complex","Kinetic enhancement of beta-oxidation by complex assembly not demonstrated"]},{"year":2011,"claim":"Demonstrated that TYSND1, not PsLon, is the key processing protease for endogenous substrates and defined a self-cleavage/degradation circuit controlling its activity.","evidence":"Reciprocal siRNA knockdown of Tysnd1 and PsLon with Western blot for substrate processing and a fatty acid beta-oxidation assay","pmids":["22002062"],"confidence":"High","gaps":["Trigger and regulation of intermolecular self-cleavage not defined","Knockdown does not exclude indirect effects on beta-oxidation","PTS1 matrix localization shown by fractionation but recruitment mechanism not detailed"]},{"year":2013,"claim":"Validated TYSND1 substrate processing and localization dependency in vivo and linked its loss to defined lipid-metabolic and developmental pathologies, and identified the cysteine endopeptidase activity plus novel substrates Phyh and Agps.","evidence":"Tysnd1 knockout mouse with substrate-processing Western blots, peroxisomal localization assays, lipidomics, and histology","pmids":["23459139"],"confidence":"High","gaps":["Direct human disease association not established","Mechanism linking processing defects to acrosomal cap defects not resolved","Whether all substrates require processing for activity versus localization not separated"]},{"year":2018,"claim":"Mapped TYSND1 into a broader peroxisomal protein interaction network regulating beta-oxidation, beginning to place the protease in its physical interactome.","evidence":"Co-immunoprecipitation combined with mass spectrometry in mammalian cells","pmids":["30378028"],"confidence":"Medium","gaps":["Single IP-MS without reciprocal validation","No functional follow-up of identified interactors","Direct versus indirect partners not distinguished"]},{"year":2023,"claim":"Confirmed LONP2/PsLon as the degrader of TYSND1, closing the proteolytic cascade, while showing TYSND1-dependent ACOX1 processing is buffered against early proteotoxic stress.","evidence":"siRNA knockdown of LONP2 with Western blot for TYSND1 and ACOX1 processing and peroxisomal phenotype analysis","pmids":["37736739"],"confidence":"Medium","gaps":["Direct degradation of TYSND1 cleavage products by LONP2 not reconstituted","Stress conditions under which the cascade becomes rate-limiting not defined","Physiological role of TYSND1 accumulation unclear"]},{"year":null,"claim":"How TYSND1 self-cleavage is triggered and integrated with substrate flux to set peroxisomal beta-oxidation rates, and whether TYSND1 variants cause human peroxisomal disease, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Regulatory trigger of autocatalytic self-cleavage unknown","No structural model of the active enzyme or substrate recognition","No reported human Mendelian disease link"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,4]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005777","term_label":"peroxisome","supporting_discovery_ids":[0,3,4]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2,4]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,4]}],"complexes":[],"partners":["ACOX1","HSD17B4","ACAA1","PHYH","AGPS","LONP2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q2T9J0","full_name":"Peroxisomal leader peptide-processing protease","aliases":["Trypsin domain-containing protein 1"],"length_aa":566,"mass_kda":59.3,"function":"Peroxisomal protease that mediates both the removal of the leader peptide from proteins containing a PTS2 target sequence and processes several PTS1-containing proteins. Catalyzes the processing of PTS1-proteins involved in the peroxisomal beta-oxidation of fatty acids","subcellular_location":"Peroxisome","url":"https://www.uniprot.org/uniprotkb/Q2T9J0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TYSND1","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TYSND1","total_profiled":1310},"omim":[{"mim_id":"617774","title":"LON PEPTIDASE 2, PEROXISOMAL; LONP2","url":"https://www.omim.org/entry/617774"},{"mim_id":"611017","title":"TRYPSIN DOMAIN-CONTAINING PROTEIN 1; TYSND1","url":"https://www.omim.org/entry/611017"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"},{"location":"Centrosome","reliability":"Uncertain"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TYSND1"},"hgnc":{"alias_symbol":["MGC34695","NET41"],"prev_symbol":[]},"alphafold":{"accession":"Q2T9J0","domains":[{"cath_id":"2.40.10.120","chopping":"2-89_128-323","consensus_level":"high","plddt":86.6359,"start":2,"end":323},{"cath_id":"2.40.10.120","chopping":"342-556","consensus_level":"medium","plddt":91.4566,"start":342,"end":556}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q2T9J0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q2T9J0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q2T9J0-F1-predicted_aligned_error_v6.png","plddt_mean":83.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TYSND1","jax_strain_url":"https://www.jax.org/strain/search?query=TYSND1"},"sequence":{"accession":"Q2T9J0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q2T9J0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q2T9J0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q2T9J0"}},"corpus_meta":[{"pmid":"17255948","id":"PMC_17255948","title":"Novel peroxisomal protease Tysnd1 processes PTS1- and PTS2-containing enzymes involved in beta-oxidation of fatty acids.","date":"2007","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/17255948","citation_count":81,"is_preprint":false},{"pmid":"22002062","id":"PMC_22002062","title":"Two proteases, trypsin domain-containing 1 (Tysnd1) and peroxisomal lon protease (PsLon), cooperatively regulate fatty acid β-oxidation in peroxisomal matrix.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22002062","citation_count":52,"is_preprint":false},{"pmid":"23459139","id":"PMC_23459139","title":"Tysnd1 deficiency in mice interferes with the peroxisomal localization of PTS2 enzymes, causing lipid metabolic abnormalities and male infertility.","date":"2013","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23459139","citation_count":29,"is_preprint":false},{"pmid":"38460933","id":"PMC_38460933","title":"Transcriptomic and proteomic study of cancer cell lines exposed to actinomycin D and nutlin-3a reveals numerous, novel candidates for p53-regulated genes.","date":"2024","source":"Chemico-biological interactions","url":"https://pubmed.ncbi.nlm.nih.gov/38460933","citation_count":11,"is_preprint":false},{"pmid":"35005033","id":"PMC_35005033","title":"Lipopolysaccharide-Induced Transcriptional Changes in LBP-Deficient Rat and Its Possible Implications for Liver Dysregulation during Sepsis.","date":"2021","source":"Journal of immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/35005033","citation_count":6,"is_preprint":false},{"pmid":"30378028","id":"PMC_30378028","title":"Identification of Peroxisomal Protein Complexes with PTS Receptors, Pex5 and Pex7, in Mammalian Cells.","date":"2018","source":"Sub-cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30378028","citation_count":3,"is_preprint":false},{"pmid":"37736739","id":"PMC_37736739","title":"Depletion of LONP2 unmasks differential requirements for peroxisomal function between cell types and in cholesterol metabolism.","date":"2023","source":"Biology direct","url":"https://pubmed.ncbi.nlm.nih.gov/37736739","citation_count":3,"is_preprint":false},{"pmid":"38727584","id":"PMC_38727584","title":"Identification of potential candidate genes for the Huoyan trait in developing Wulong goose embryos by transcriptomic analysis.","date":"2024","source":"British poultry science","url":"https://pubmed.ncbi.nlm.nih.gov/38727584","citation_count":2,"is_preprint":false},{"pmid":"41882721","id":"PMC_41882721","title":"Pharmacogenomic study of the effects of saxagliptin on glucose control and hypoglycemic events.","date":"2026","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/41882721","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7457,"output_tokens":1969,"usd":0.025953,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8903,"output_tokens":2526,"usd":0.053832,"stage2_stop_reason":"end_turn"},"total_usd":0.079785,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"Tysnd1 is a peroxisomal protease responsible for both the removal of the N-terminal PTS2 leader peptide from PTS2-containing proteins (e.g., prethiolase Acaa1) and the specific limited cleavage of PTS1-containing peroxisomal beta-oxidation enzymes (e.g., Acox1, Hsd17b4, ScpX). Tysnd1 itself undergoes autocatalytic processing through removal of a presumably inhibitory N-terminal fragment, and its expression is induced by the PPARα agonist bezafibrate.\",\n      \"method\": \"Biochemical characterization of a previously uncharacterized protein; in vitro protease assays; identification of substrates; expression induction assay with bezafibrate\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct enzymatic assays identifying substrates and autocatalytic processing, replicated in subsequent independent studies\",\n      \"pmids\": [\"17255948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Tysnd1-mediated proteolytic processing of peroxisomal beta-oxidation enzymes was proposed to promote their assembly into a supramolecular complex to enhance the rate of beta-oxidation.\",\n      \"method\": \"Biochemical characterization and substrate identification; model proposed based on experimental data\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — model supported by substrate identification and processing assays in a single lab, but supramolecular complex assembly not directly reconstituted\",\n      \"pmids\": [\"17255948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Tysnd1 knockdown, but not PsLon (peroxisomal Lon protease) knockdown, results in accumulation of endogenous beta-oxidation enzymes in their premature (unprocessed) form, establishing Tysnd1 as the key processing protease. The proteolytic activity of oligomeric Tysnd1 is regulated by intermolecular self-cleavage converting the 60-kDa form into 15- and 45-kDa chains, which are then preferentially degraded by PsLon. Peroxisomal beta-oxidation of very long-chain fatty acids was significantly decreased by Tysnd1 knockdown and partially lowered by PsLon knockdown.\",\n      \"method\": \"siRNA knockdown of Tysnd1 and PsLon; Western blot for substrate processing; fatty acid beta-oxidation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal knockdown experiments with defined phenotypic readouts, multiple orthogonal methods (Western blot, functional beta-oxidation assay), single lab\",\n      \"pmids\": [\"22002062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Tysnd1 is a serine protease-like domain-containing peroxisomal matrix protein that harbors a PTS1 targeting sequence, localizing it to the peroxisomal matrix.\",\n      \"method\": \"Sequence analysis and biochemical fractionation/localization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization established by fractionation and domain analysis, consistent across multiple studies\",\n      \"pmids\": [\"22002062\", \"17255948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In vivo, Tysnd1 is a peroxisomal cysteine endopeptidase that directly processes PTS2-containing prethiolase Acaa1, and PTS1-containing Acox1, Hsd17b4, and ScpX. Novel substrates Phyh and Agps (PTS2-containing proteins) were identified. Loss of Tysnd1 interferes with the peroxisomal localization of Acaa1, Phyh, and Agps, causing lipid metabolic abnormalities (altered plasmalogen composition), male infertility due to acrosomal cap defects in spermatozoa, and liver dysfunction upon phytol administration resembling mild Zellweger syndrome spectrum.\",\n      \"method\": \"Tysnd1 knockout (Tysnd1−/−) mouse model; analysis of substrate processing by Western blot; peroxisomal localization assays; lipidomics; histology\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with multiple orthogonal phenotypic and biochemical readouts, in vivo validation of enzymatic substrates and localization dependency\",\n      \"pmids\": [\"23459139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Tysnd1 participates in a protein interaction network regulating peroxisomal fatty acid beta-oxidation, as revealed by immunoprecipitation-mass spectrometry analysis of Tysnd1 binding partners in mammalian cells.\",\n      \"method\": \"Co-immunoprecipitation combined with mass spectrometry (IP-MS)\",\n      \"journal\": \"Sub-cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single IP-MS experiment; no reciprocal validation or functional follow-up described in the abstract\",\n      \"pmids\": [\"30378028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LONP2 (PsLon) depletion causes accumulation of its substrate TYSND1 protease in peroxisomes, consistent with LONP2 acting as the degrader of Tysnd1 cleavage products. Despite TYSND1 accumulation, TYSND1-dependent ACOX1 processing appeared normal at early stages of peroxisomal proteotoxic stress, indicating the regulatory relationship between LONP2 and TYSND1 in peroxisomal protein quality control.\",\n      \"method\": \"siRNA knockdown of LONP2; Western blot for TYSND1 and ACOX1 processing; peroxisomal phenotype analysis\",\n      \"journal\": \"Biology direct\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with direct measurement of substrate (TYSND1) accumulation and downstream processing, consistent with prior mechanistic model\",\n      \"pmids\": [\"37736739\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TYSND1 is a peroxisomal matrix cysteine/serine endopeptidase (localized via a PTS1 signal) that processes both PTS1-containing beta-oxidation enzymes (Acox1, Hsd17b4, ScpX) and cleaves the N-terminal PTS2 targeting sequences from PTS2 precursor proteins (Acaa1, Phyh, Agps); this processing is required for correct peroxisomal localization and activity of substrate enzymes, thereby regulating peroxisomal fatty acid beta-oxidation. TYSND1 activity is itself regulated by intermolecular autocatalytic self-cleavage (converting the active 60-kDa form to inactive 15- and 45-kDa chains), with the cleavage products subsequently degraded by the peroxisomal Lon protease LONP2/PsLon, forming a proteolytic regulatory cascade.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TYSND1 is a peroxisomal matrix endopeptidase that processes the enzymes of the fatty acid beta-oxidation pathway and thereby governs their correct localization and activity [#0, #4]. Targeted to the peroxisomal matrix by a PTS1 signal, it performs two distinct proteolytic functions: it removes the N-terminal PTS2 leader peptide from PTS2-containing precursors (Acaa1/prethiolase, and the substrates Phyh and Agps) and carries out specific limited cleavage of PTS1-containing beta-oxidation enzymes (Acox1, Hsd17b4, ScpX) [#0, #4]. This processing is required for the proper peroxisomal localization of substrates such as Acaa1, Phyh, and Agps, and its activity sustains beta-oxidation of very long-chain fatty acids [#2, #4]. Genetic loss of Tysnd1 in mice produces unprocessed substrate accumulation, altered plasmalogen composition, male infertility from acrosomal cap defects, and phytol-induced liver dysfunction resembling the mild Zellweger syndrome spectrum [#4]. TYSND1 is itself regulated by intermolecular autocatalytic self-cleavage that converts the active 60-kDa form into inactive 15- and 45-kDa chains, which are then degraded by the peroxisomal Lon protease LONP2/PsLon, establishing a proteolytic regulatory cascade for peroxisomal protein quality control [#2, #6]. Its expression is induced by the PPARalpha agonist bezafibrate [#0].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established TYSND1 as a peroxisomal protease performing the dual reactions needed to mature beta-oxidation enzymes, answering how PTS2 leaders are removed and PTS1 enzymes are limited-cleaved within the peroxisome.\",\n      \"evidence\": \"Biochemical characterization with in vitro protease assays and substrate identification, plus bezafibrate induction assay\",\n      \"pmids\": [\"17255948\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic class (cysteine vs serine) not definitively resolved at this stage\", \"In vivo physiological relevance not yet tested\", \"Functional consequence of autocatalytic processing not quantified\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Proposed that TYSND1-mediated processing promotes assembly of beta-oxidation enzymes into a supramolecular complex to accelerate the pathway, framing processing as functional rather than merely targeting-related.\",\n      \"evidence\": \"Model proposed from substrate identification and processing assays\",\n      \"pmids\": [\"17255948\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Supramolecular complex assembly not directly reconstituted\", \"No structural evidence for the proposed complex\", \"Kinetic enhancement of beta-oxidation by complex assembly not demonstrated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated that TYSND1, not PsLon, is the key processing protease for endogenous substrates and defined a self-cleavage/degradation circuit controlling its activity.\",\n      \"evidence\": \"Reciprocal siRNA knockdown of Tysnd1 and PsLon with Western blot for substrate processing and a fatty acid beta-oxidation assay\",\n      \"pmids\": [\"22002062\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger and regulation of intermolecular self-cleavage not defined\", \"Knockdown does not exclude indirect effects on beta-oxidation\", \"PTS1 matrix localization shown by fractionation but recruitment mechanism not detailed\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Validated TYSND1 substrate processing and localization dependency in vivo and linked its loss to defined lipid-metabolic and developmental pathologies, and identified the cysteine endopeptidase activity plus novel substrates Phyh and Agps.\",\n      \"evidence\": \"Tysnd1 knockout mouse with substrate-processing Western blots, peroxisomal localization assays, lipidomics, and histology\",\n      \"pmids\": [\"23459139\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct human disease association not established\", \"Mechanism linking processing defects to acrosomal cap defects not resolved\", \"Whether all substrates require processing for activity versus localization not separated\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mapped TYSND1 into a broader peroxisomal protein interaction network regulating beta-oxidation, beginning to place the protease in its physical interactome.\",\n      \"evidence\": \"Co-immunoprecipitation combined with mass spectrometry in mammalian cells\",\n      \"pmids\": [\"30378028\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single IP-MS without reciprocal validation\", \"No functional follow-up of identified interactors\", \"Direct versus indirect partners not distinguished\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Confirmed LONP2/PsLon as the degrader of TYSND1, closing the proteolytic cascade, while showing TYSND1-dependent ACOX1 processing is buffered against early proteotoxic stress.\",\n      \"evidence\": \"siRNA knockdown of LONP2 with Western blot for TYSND1 and ACOX1 processing and peroxisomal phenotype analysis\",\n      \"pmids\": [\"37736739\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct degradation of TYSND1 cleavage products by LONP2 not reconstituted\", \"Stress conditions under which the cascade becomes rate-limiting not defined\", \"Physiological role of TYSND1 accumulation unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TYSND1 self-cleavage is triggered and integrated with substrate flux to set peroxisomal beta-oxidation rates, and whether TYSND1 variants cause human peroxisomal disease, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Regulatory trigger of autocatalytic self-cleavage unknown\", \"No structural model of the active enzyme or substrate recognition\", \"No reported human Mendelian disease link\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005777\", \"supporting_discovery_ids\": [0, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ACOX1\", \"HSD17B4\", \"ACAA1\", \"PHYH\", \"AGPS\", \"LONP2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":6,"faith_total":6,"faith_pct":100.0}}