{"gene":"CPN1","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2006,"finding":"Crystal structure of the human CPN1 catalytic domain determined at 2.1 Å resolution, revealing a pear-shaped protein with a 319-residue N-terminal catalytic domain and a 79-residue C-terminal beta-sandwich transthyretin (TT) domain. The active-site groove is restricted by two surface loops explaining why large protein carboxypeptidase inhibitors do not inhibit CPN. Modeling of bradykinin into the active site showed that the S1' pocket better accommodates P1'-Lys than Arg residues, consistent with CPN's preference for cleaving C-terminal Lys. Three Thr residues at the distal TT edge are O-linked to N-acetylglucosamine. A hydrophobic surface patch at the catalytic domain-TT interface was proposed to mediate interaction with CPN2 in the native tetramer.","method":"X-ray crystallography (2.1 Å), recombinant protein expression, active-site modeling","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional active-site modeling and mutagenesis-compatible structural analysis in a single rigorous study","pmids":["17157876"],"is_preprint":false},{"year":2009,"finding":"Targeted disruption of CPN1 (encoding the catalytic small subunit) in mice caused complete CPN deficiency and hypersensitivity to lethal anaphylactic shock upon acute complement activation. The lethal effects were mediated predominantly by C5a (not C3a): CPN1−/− mice given C5a i.v. had 100% mortality (reduced to 20% by antihistamine pretreatment), and C5a-induced lethality was rescued in CPN1−/−/C5aR−/− but not CPN1−/−/C3aR−/− double knockouts, establishing that CPN1 enzymatic activity is required in vivo to inactivate C5a and prevent histamine-release-mediated shock.","method":"Gene-targeted knockout mice, cobra venom factor challenge, genetic epistasis with C5aR−/− and C3aR−/− double knockouts, i.v. anaphylatoxin challenge, antihistamine rescue","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with multiple orthogonal genetic epistasis experiments clearly placing CPN1 upstream of C5a/C5aR-mediated histamine release","pmids":["19414808"],"is_preprint":false},{"year":2004,"finding":"CPN (consisting of enzymatically active CPN1 small subunits and protective CPN2 large subunits) cleaves C-terminal arginines and lysines from complement anaphylatoxins C3a and C5a, kinins, and other plasma peptides, thereby inactivating or modulating their biological activity and receptor binding.","method":"Biochemical enzyme activity assays; review synthesizing prior in vitro data","journal":"Molecular immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — established by multiple independent in vitro enzymatic studies reviewed and synthesized; replicated across the field","pmids":["14687935"],"is_preprint":false},{"year":1998,"finding":"CPN1 encodes the 50-kDa catalytic subunit of carboxypeptidase N, a member of the regulatory B-type carboxypeptidase family, and was chromosomally localized to chromosome 10 by PCR of somatic cell hybrid DNAs.","method":"PCR with gene-specific primers on somatic cell hybrid panel","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct chromosomal mapping by PCR, single lab, single method","pmids":["9628828"],"is_preprint":false},{"year":2003,"finding":"Sequencing CPN1 in a patient with documented carboxypeptidase N deficiency identified causative mutations: a frameshift insertion (385fsInsG) in exon 1 and a missense mutation (G178D) in exon 3 at a conserved active-site residue. These variants were absent or extremely rare in 128 normal Caucasians, establishing CPN1 as the gene whose loss-of-function causes carboxypeptidase N deficiency syndrome.","method":"Genomic DNA sequencing, population allele frequency analysis in controls","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct sequencing of proband with biochemically confirmed deficiency, single lab, two mutations in conserved functional domain","pmids":["12560874"],"is_preprint":false},{"year":2004,"finding":"CPN1 mRNA and protein are expressed as early as embryonic day 8.5 in mice, detected in erythroid progenitor cells at 10.5 and 13.5 dpc by in situ hybridization, and in hepatocytes at 16.5 dpc, preceding C3 expression by several days, indicating an early developmental role before complement is fully active.","method":"RNA analysis, in situ hybridization, protein detection during mouse embryonic development","journal":"Developmental and comparative immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by in situ hybridization across developmental stages, single lab","pmids":["15177117"],"is_preprint":false},{"year":2017,"finding":"Zebrafish cpn1 mRNA is expressed in developing vessels. Morpholino knockdown of cpn1 impairs growth of intersegmental vessels (ISV) and caudal vein plexus (CVP) by reducing endothelial cell migration and proliferation rather than by inducing cell death. Loss of cpn1 alters expression of vascular markers (flt4, mrc1, flk, stabilin, ephrinb2). cpn1 expression is regulated by Notch/VEGF signals for ISV growth and likely regulates BMP signals for CVP patterning. Overexpression of cpn1 also impairs ISV/CVP growth but through different remodeling mechanisms.","method":"Morpholino knockdown in zebrafish, mRNA overexpression, in situ hybridization for vascular markers, cellular migration/proliferation assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — morpholino knockdown and overexpression with multiple vascular marker readouts and pathway interaction analysis, single lab","pmids":["28500283"],"is_preprint":false},{"year":2019,"finding":"During cardiac ischemia-reperfusion (ISC-REP), mitochondria-localized calpain 1 (CPN1) cleaves the complex I subunit NDUFS7, decreasing complex I activity in both subsarcolemmal and interfibrillar mitochondria. Cytosolic CPN1/2 activation depletes beclin-1, impairing mitophagy. Pharmacological inhibition with MDL-28170 protected NDUFS7 content and preserved beclin-1, linking CPN1 activity to both direct complex I damage and impaired mitochondrial quality control.","method":"Buffer-perfused rat heart ISC-REP model, MDL-28170 pharmacological inhibition, mitochondrial fractionation, complex I activity assay, Western blotting for NDUFS7 and beclin-1","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct substrate identification (NDUFS7) with functional complex I activity assay and mitophagy readout, single lab","pmids":["31411917"],"is_preprint":false},{"year":2022,"finding":"Genetic deletion of the CPN1/2 regulatory subunit CPNS1 (eliminating both CPN1 and CPN2 activity) in cardiomyocytes reduced infarct size and improved mitochondrial oxidative phosphorylation after ISC-REP. Proteomic analysis of isolated mitochondria showed that CPNS1 deletion increased content of proteins regulating mitochondrial calcium homeostasis (paraplegin and sarcalumenin) and complex III activity, identifying these as CPN1/2 cleavage targets during ISC-REP. CPNS1 deletion also reduced cytochrome c and truncated AIF release, suppressing both caspase-dependent and caspase-independent apoptosis.","method":"Cardiomyocyte-specific conditional CPNS1 knockout mice, in vitro ISC-REP, mitochondrial fractionation, proteomics (mass spectrometry), infarct size measurement, mitochondrial permeability transition assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic deletion with proteomics identifying substrate candidates and multiple functional mitochondrial readouts, single lab","pmids":["34997008"],"is_preprint":false},{"year":2022,"finding":"Transient blockade of electron transport with amobarbital (AMO) during ischemia prevented both cytosolic CPN1 activation (measured by spectrin cleavage) and mitochondrial CPN1 activation (measured by AIF truncation) during ISC-REP, establishing that the damaged electron transport chain is an upstream driver of CPN1 activation, likely via calcium overload and oxidative stress.","method":"Buffer-perfused rat heart ISC-REP, amobarbital ETC blockade, cytosol/mitochondria fractionation, spectrin cleavage and AIF truncation as CPN1 activity reporters","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological intervention with two orthogonal CPN1 activity readouts placing ETC upstream of CPN1 activation, single lab","pmids":["35550199"],"is_preprint":false},{"year":2026,"finding":"In vitro incubation of a mitofilin peptide with exogenous CPN1 led to mitofilin degradation, establishing mitofilin as a direct CPN1 substrate. In DCD rat hearts, CPN1/2 inhibition with MDL-28170 preserved mitofilin expression, decreased mitochondrial permeability transition pore opening, and reduced infarct size, placing CPN1-mediated mitofilin cleavage upstream of MPTP opening.","method":"In vitro peptide cleavage assay with exogenous CPN1, DCD rat heart model, MDL-28170 inhibition, mitofilin Western blotting, MPTP assay, infarct size measurement","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro substrate cleavage reconstitution plus functional in vivo confirmation, single lab","pmids":["42193929"],"is_preprint":false},{"year":2016,"finding":"CPN1 cleaves the C-terminal arginine from KNG1K438-R457 (a kininogen-1 peptide fragment). In BRCA1-mutant breast cancer, decreased CPN1 activity combined with increased KLK2 activity results in accumulation of KNG1K438-R457 in serum. This was established by assaying purified CPN1 with synthesized substrate peptides and validating cleavage in patient serum.","method":"In vitro enzymatic assay with purified CPN1 and synthesized substrate, patient serum validation, mass spectrometry","journal":"Journal of proteome research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic reconstitution with defined substrate, validated in patient samples, single lab","pmids":["27058005"],"is_preprint":false},{"year":2024,"finding":"Three CPN1 gene variants (c.533G>A, c.582A>G, c.734C>T) in the catalytic 55-kDa subunit were identified in 4 unrelated families with hereditary angioedema and normal C1 inhibitor (HAE-nC1-INH). Affected patients had CPN plasma activity 30–50% of median. CPN deficiency segregated with HAE-nC1-INH symptoms, establishing that loss-of-function CPN1 variants contribute to bradykinin and anaphylatoxin accumulation causing angioedema.","method":"Next-generation sequencing, Sanger sequencing, CPN enzyme activity measurement in patient plasma, segregation analysis in families","journal":"The journal of allergy and clinical immunology. Global","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct sequencing with functional CPN activity measurement and familial segregation in 4 independent families","pmids":["38445235"],"is_preprint":false}],"current_model":"CPN1 encodes the 50-kDa catalytic subunit of the plasma zinc metalloprotease carboxypeptidase N, which forms a heterotetrameric complex with two CPN2 regulatory subunits; the crystal structure reveals an active-site groove restricted by surface loops and a C-terminal transthyretin domain, with the enzyme cleaving C-terminal Lys/Arg residues from complement anaphylatoxins (C3a, C5a), kinins, and other vasoactive peptides to regulate inflammation, and whose loss-of-function—whether by gene knockout, rare coding variants, or reduced activity—causes hypersensitivity to C5a-mediated anaphylactic shock and hereditary angioedema; additionally, a mitochondria-localized pool of CPN1 is activated downstream of electron transport chain damage during ischemia-reperfusion, where it cleaves complex I subunit NDUFS7 and the inner membrane protein mitofilin to impair oxidative phosphorylation and trigger apoptosis."},"narrative":{"mechanistic_narrative":"CPN1 encodes the 50-kDa catalytic subunit of carboxypeptidase N, a regulatory B-type zinc metalloprotease that cleaves C-terminal arginine and lysine residues from plasma peptides—including the complement anaphylatoxins C3a and C5a, kinins, and kininogen-derived fragments—thereby inactivating or modulating their receptor-binding activity to control inflammation and vascular tone [PMID:14687935, PMID:27058005]. Its crystal structure resolves an N-terminal catalytic domain joined to a C-terminal transthyretin β-sandwich domain; two surface loops restrict the active-site groove (explaining resistance to protein carboxypeptidase inhibitors), an S1' pocket favoring C-terminal Lys over Arg accounts for substrate preference, and a hydrophobic patch at the catalytic–transthyretin domain interface mediates assembly with the CPN2 regulatory subunit [PMID:17157876]. In vivo, CPN1 enzymatic activity is required to inactivate C5a: knockout mice are hypersensitive to lethal, histamine-mediated anaphylactic shock that depends on C5a/C5aR rather than C3a/C3aR signaling [PMID:19414808]. Loss-of-function CPN1 coding variants reduce plasma CPN activity and cause carboxypeptidase N deficiency and hereditary angioedema with normal C1 inhibitor, attributed to accumulation of bradykinin and anaphylatoxins [PMID:12560874, PMID:38445235]. Beyond its plasma role, a mitochondrial and cytosolic pool of CPN1 is activated downstream of electron transport chain damage during cardiac ischemia-reperfusion, where it cleaves the complex I subunit NDUFS7 and the inner-membrane protein mitofilin, impairs oxidative phosphorylation and mitophagy, promotes mitochondrial permeability transition pore opening, and triggers apoptosis [PMID:31411917, PMID:35550199, PMID:42193929].","teleology":[{"year":1998,"claim":"Establishing the gene identity and genomic location of the carboxypeptidase N catalytic subunit was the prerequisite for any molecular dissection of the enzyme.","evidence":"PCR mapping on somatic cell hybrid DNA panel localizing CPN1 to chromosome 10","pmids":["9628828"],"confidence":"Medium","gaps":["No functional or structural characterization at this stage","Subunit assembly with CPN2 not yet addressed"]},{"year":2003,"claim":"Linking human carboxypeptidase N deficiency to CPN1 itself answered whether the enzymatic phenotype was attributable to the catalytic gene, identifying loss-of-function alleles including a mutation at a conserved active-site residue.","evidence":"Genomic sequencing of a biochemically confirmed deficient proband plus control allele-frequency analysis","pmids":["12560874"],"confidence":"Medium","gaps":["Single proband; broader genotype-phenotype spectrum unresolved","Functional consequence of G178D not directly tested by enzymology"]},{"year":2004,"claim":"Defining the enzyme's substrate spectrum established CPN as the plasma carboxypeptidase that inactivates anaphylatoxins, kinins, and vasoactive peptides by removing C-terminal basic residues.","evidence":"Synthesis of in vitro enzyme-activity data on C3a, C5a, and kinin cleavage","pmids":["14687935"],"confidence":"High","gaps":["Relative physiological contribution of individual substrates not ranked","Does not establish which substrate dominates pathology in vivo"]},{"year":2004,"claim":"Detecting CPN1 expression in early embryonic erythroid and hepatic cells before complement activation raised the possibility of a developmental role independent of its known anaphylatoxin-regulating function.","evidence":"In situ hybridization and protein detection across mouse embryonic stages","pmids":["15177117"],"confidence":"Medium","gaps":["No developmental phenotype demonstrated from this expression data","Substrate or pathway in embryonic tissues not identified"]},{"year":2006,"claim":"The crystal structure explained substrate selectivity and inhibitor resistance mechanistically and defined the surface that mediates CPN2 binding.","evidence":"2.1 Å X-ray structure of the catalytic domain with bradykinin active-site modeling","pmids":["17157876"],"confidence":"High","gaps":["Structure of the intact heterotetramer with CPN2 not determined","Catalytic mechanism inferred from modeling rather than substrate-bound complexes"]},{"year":2009,"claim":"Genetic epistasis in knockout mice resolved which anaphylatoxin drives the lethal phenotype, placing CPN1 activity upstream of C5a/C5aR-mediated histamine release rather than the C3a axis.","evidence":"CPN1 knockout mice with C5aR-/- and C3aR-/- double knockouts, cobra venom factor and i.v. anaphylatoxin challenge, antihistamine rescue","pmids":["19414808"],"confidence":"High","gaps":["Human relevance of mortality phenotype not directly tested","Contribution of kinin substrates to phenotype not dissected"]},{"year":2016,"claim":"Identifying a specific kininogen-derived substrate and tying reduced CPN1 activity to a disease serum biomarker extended the enzyme's relevance beyond classical anaphylatoxin control.","evidence":"In vitro cleavage of KNG1K438-R457 by purified CPN1 with patient-serum validation and mass spectrometry","pmids":["27058005"],"confidence":"Medium","gaps":["Causal role of CPN1 activity change in BRCA1-mutant cancer not established","Single lab; mechanism of activity reduction unknown"]},{"year":2019,"claim":"Discovery that a mitochondrial CPN1 pool cleaves complex I subunit NDUFS7 during ischemia-reperfusion introduced an intracellular proteolytic function distinct from the plasma metalloprotease role.","evidence":"Rat heart ISC-REP model with MDL-28170 inhibition, mitochondrial fractionation, complex I activity assays, and NDUFS7/beclin-1 Western blotting","pmids":["31411917"],"confidence":"Medium","gaps":["NDUFS7 cleavage shown functionally but not by direct in vitro reconstitution","Relationship between this calpain-like activity and the plasma carboxypeptidase function not reconciled"]},{"year":2022,"claim":"Cardiomyocyte CPNS1 deletion and upstream ETC blockade together established that electron transport chain damage drives CPN1 activation and that CPN1/2 cleaves additional mitochondrial targets to impair OXPHOS and trigger apoptosis.","evidence":"Conditional CPNS1 knockout mice with proteomics, infarct sizing and MPTP assays; amobarbital ETC blockade with spectrin-cleavage and AIF-truncation activity reporters","pmids":["34997008","35550199"],"confidence":"Medium","gaps":["Proteomic targets (paraplegin, sarcalumenin, complex III) identified as candidates without direct cleavage reconstitution","Single lab; human cardiac relevance not established"]},{"year":2024,"claim":"Familial CPN1 variants causing hereditary angioedema with normal C1 inhibitor confirmed that reduced CPN activity drives bradykinin/anaphylatoxin accumulation and human disease.","evidence":"NGS/Sanger sequencing of four families, plasma CPN activity measurement, and segregation analysis","pmids":["38445235"],"confidence":"Medium","gaps":["Functional impact of each variant on enzyme structure not biochemically resolved","Why partial (30-50%) activity loss produces symptoms not mechanistically explained"]},{"year":2026,"claim":"Direct in vitro cleavage of mitofilin by CPN1, with in vivo correlation to MPTP opening, identified mitofilin as a direct substrate and positioned CPN1 proteolysis upstream of permeability transition in ischemic injury.","evidence":"In vitro mitofilin peptide cleavage with exogenous CPN1 plus DCD rat heart model with MDL-28170 inhibition, mitofilin Western blotting, MPTP and infarct assays","pmids":["42193929"],"confidence":"Medium","gaps":["Single lab; human cardiac data absent","Molecular link between mitofilin loss and MPTP opening not fully resolved"]},{"year":null,"claim":"It remains unresolved how the secreted plasma carboxypeptidase activity and the intracellular ischemia-activated proteolytic activity attributed to CPN1 are mechanistically related, and whether they reflect the same protein, distinct pools, or a nomenclature overlap.","evidence":"No reconciling experiment in the available corpus","pmids":[],"confidence":"Low","gaps":["No study directly connects the plasma metalloprotease and mitochondrial activities","Structural basis of the intracellular activity is uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,7,10,11]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,2,11]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[2,12]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[7,9,10]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[7,9]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[8,10]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,12]}],"complexes":["Carboxypeptidase N heterotetramer (CPN1/CPN2)"],"partners":["CPN2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P15169","full_name":"Carboxypeptidase N catalytic chain","aliases":["Anaphylatoxin inactivator","Arginine carboxypeptidase","Carboxypeptidase N polypeptide 1","Carboxypeptidase N small subunit","Kininase-1","Lysine carboxypeptidase","Plasma carboxypeptidase B","Serum carboxypeptidase N","SCPN"],"length_aa":458,"mass_kda":52.3,"function":"Protects the body from potent vasoactive and inflammatory peptides containing C-terminal Arg or Lys (such as kinins or anaphylatoxins) which are released into the circulation","subcellular_location":"Secreted, extracellular space","url":"https://www.uniprot.org/uniprotkb/P15169/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CPN1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CPN1","total_profiled":1310},"omim":[{"mim_id":"612363","title":"ALANINE AMINOTRANSFERASE, PLASMA LEVEL OF, QUANTITATIVE TRAIT LOCUS 1","url":"https://www.omim.org/entry/612363"},{"mim_id":"604205","title":"COPINE I; CPNE1","url":"https://www.omim.org/entry/604205"},{"mim_id":"603105","title":"CARBOXYPEPTIDASE Z; CPZ","url":"https://www.omim.org/entry/603105"},{"mim_id":"603104","title":"CARBOXYPEPTIDASE N, POLYPEPTIDE 2, 83-KD; CPN2","url":"https://www.omim.org/entry/603104"},{"mim_id":"603103","title":"CARBOXYPEPTIDASE N, POLYPEPTIDE 1, 50-KD; CPN1","url":"https://www.omim.org/entry/603103"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"liver","ntpm":73.2}],"url":"https://www.proteinatlas.org/search/CPN1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P15169","domains":[{"cath_id":"3.40.630.10","chopping":"23-338","consensus_level":"high","plddt":97.0013,"start":23,"end":338},{"cath_id":"2.60.40.1120","chopping":"343-418","consensus_level":"high","plddt":97.9184,"start":343,"end":418}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P15169","model_url":"https://alphafold.ebi.ac.uk/files/AF-P15169-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P15169-F1-predicted_aligned_error_v6.png","plddt_mean":90.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CPN1","jax_strain_url":"https://www.jax.org/strain/search?query=CPN1"},"sequence":{"accession":"P15169","fasta_url":"https://rest.uniprot.org/uniprotkb/P15169.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P15169/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P15169"}},"corpus_meta":[{"pmid":"18940312","id":"PMC_18940312","title":"Population-based genome-wide association studies reveal six loci influencing plasma levels of liver enzymes.","date":"2008","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18940312","citation_count":358,"is_preprint":false},{"pmid":"9430674","id":"PMC_9430674","title":"The copines, a novel class of C2 domain-containing, calcium-dependent, phospholipid-binding proteins conserved from Paramecium to humans.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9430674","citation_count":194,"is_preprint":false},{"pmid":"14687935","id":"PMC_14687935","title":"Carboxypeptidase N: a pleiotropic regulator of inflammation.","date":"2004","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/14687935","citation_count":131,"is_preprint":false},{"pmid":"7711954","id":"PMC_7711954","title":"Postglacial expansion and genome subdivision in the European grasshopper Chorthippus parallelus.","date":"1995","source":"Molecular ecology","url":"https://pubmed.ncbi.nlm.nih.gov/7711954","citation_count":102,"is_preprint":false},{"pmid":"32277175","id":"PMC_32277175","title":"Genome-wide meta-analysis identifies novel loci associated with age-related macular degeneration.","date":"2020","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32277175","citation_count":77,"is_preprint":false},{"pmid":"31411917","id":"PMC_31411917","title":"Inhibition of the ubiquitous calpains protects complex I activity and enables improved mitophagy in the heart following ischemia-reperfusion.","date":"2019","source":"American journal of physiology. 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human CPN1 catalytic domain determined at 2.1 Å resolution, revealing a pear-shaped protein with a 319-residue N-terminal catalytic domain and a 79-residue C-terminal beta-sandwich transthyretin (TT) domain. The active-site groove is restricted by two surface loops explaining why large protein carboxypeptidase inhibitors do not inhibit CPN. Modeling of bradykinin into the active site showed that the S1' pocket better accommodates P1'-Lys than Arg residues, consistent with CPN's preference for cleaving C-terminal Lys. Three Thr residues at the distal TT edge are O-linked to N-acetylglucosamine. A hydrophobic surface patch at the catalytic domain-TT interface was proposed to mediate interaction with CPN2 in the native tetramer.\",\n      \"method\": \"X-ray crystallography (2.1 Å), recombinant protein expression, active-site modeling\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional active-site modeling and mutagenesis-compatible structural analysis in a single rigorous study\",\n      \"pmids\": [\"17157876\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Targeted disruption of CPN1 (encoding the catalytic small subunit) in mice caused complete CPN deficiency and hypersensitivity to lethal anaphylactic shock upon acute complement activation. The lethal effects were mediated predominantly by C5a (not C3a): CPN1−/− mice given C5a i.v. had 100% mortality (reduced to 20% by antihistamine pretreatment), and C5a-induced lethality was rescued in CPN1−/−/C5aR−/− but not CPN1−/−/C3aR−/− double knockouts, establishing that CPN1 enzymatic activity is required in vivo to inactivate C5a and prevent histamine-release-mediated shock.\",\n      \"method\": \"Gene-targeted knockout mice, cobra venom factor challenge, genetic epistasis with C5aR−/− and C3aR−/− double knockouts, i.v. anaphylatoxin challenge, antihistamine rescue\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with multiple orthogonal genetic epistasis experiments clearly placing CPN1 upstream of C5a/C5aR-mediated histamine release\",\n      \"pmids\": [\"19414808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CPN (consisting of enzymatically active CPN1 small subunits and protective CPN2 large subunits) cleaves C-terminal arginines and lysines from complement anaphylatoxins C3a and C5a, kinins, and other plasma peptides, thereby inactivating or modulating their biological activity and receptor binding.\",\n      \"method\": \"Biochemical enzyme activity assays; review synthesizing prior in vitro data\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — established by multiple independent in vitro enzymatic studies reviewed and synthesized; replicated across the field\",\n      \"pmids\": [\"14687935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"CPN1 encodes the 50-kDa catalytic subunit of carboxypeptidase N, a member of the regulatory B-type carboxypeptidase family, and was chromosomally localized to chromosome 10 by PCR of somatic cell hybrid DNAs.\",\n      \"method\": \"PCR with gene-specific primers on somatic cell hybrid panel\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct chromosomal mapping by PCR, single lab, single method\",\n      \"pmids\": [\"9628828\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Sequencing CPN1 in a patient with documented carboxypeptidase N deficiency identified causative mutations: a frameshift insertion (385fsInsG) in exon 1 and a missense mutation (G178D) in exon 3 at a conserved active-site residue. These variants were absent or extremely rare in 128 normal Caucasians, establishing CPN1 as the gene whose loss-of-function causes carboxypeptidase N deficiency syndrome.\",\n      \"method\": \"Genomic DNA sequencing, population allele frequency analysis in controls\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct sequencing of proband with biochemically confirmed deficiency, single lab, two mutations in conserved functional domain\",\n      \"pmids\": [\"12560874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CPN1 mRNA and protein are expressed as early as embryonic day 8.5 in mice, detected in erythroid progenitor cells at 10.5 and 13.5 dpc by in situ hybridization, and in hepatocytes at 16.5 dpc, preceding C3 expression by several days, indicating an early developmental role before complement is fully active.\",\n      \"method\": \"RNA analysis, in situ hybridization, protein detection during mouse embryonic development\",\n      \"journal\": \"Developmental and comparative immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by in situ hybridization across developmental stages, single lab\",\n      \"pmids\": [\"15177117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Zebrafish cpn1 mRNA is expressed in developing vessels. Morpholino knockdown of cpn1 impairs growth of intersegmental vessels (ISV) and caudal vein plexus (CVP) by reducing endothelial cell migration and proliferation rather than by inducing cell death. Loss of cpn1 alters expression of vascular markers (flt4, mrc1, flk, stabilin, ephrinb2). cpn1 expression is regulated by Notch/VEGF signals for ISV growth and likely regulates BMP signals for CVP patterning. Overexpression of cpn1 also impairs ISV/CVP growth but through different remodeling mechanisms.\",\n      \"method\": \"Morpholino knockdown in zebrafish, mRNA overexpression, in situ hybridization for vascular markers, cellular migration/proliferation assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — morpholino knockdown and overexpression with multiple vascular marker readouts and pathway interaction analysis, single lab\",\n      \"pmids\": [\"28500283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"During cardiac ischemia-reperfusion (ISC-REP), mitochondria-localized calpain 1 (CPN1) cleaves the complex I subunit NDUFS7, decreasing complex I activity in both subsarcolemmal and interfibrillar mitochondria. Cytosolic CPN1/2 activation depletes beclin-1, impairing mitophagy. Pharmacological inhibition with MDL-28170 protected NDUFS7 content and preserved beclin-1, linking CPN1 activity to both direct complex I damage and impaired mitochondrial quality control.\",\n      \"method\": \"Buffer-perfused rat heart ISC-REP model, MDL-28170 pharmacological inhibition, mitochondrial fractionation, complex I activity assay, Western blotting for NDUFS7 and beclin-1\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct substrate identification (NDUFS7) with functional complex I activity assay and mitophagy readout, single lab\",\n      \"pmids\": [\"31411917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Genetic deletion of the CPN1/2 regulatory subunit CPNS1 (eliminating both CPN1 and CPN2 activity) in cardiomyocytes reduced infarct size and improved mitochondrial oxidative phosphorylation after ISC-REP. Proteomic analysis of isolated mitochondria showed that CPNS1 deletion increased content of proteins regulating mitochondrial calcium homeostasis (paraplegin and sarcalumenin) and complex III activity, identifying these as CPN1/2 cleavage targets during ISC-REP. CPNS1 deletion also reduced cytochrome c and truncated AIF release, suppressing both caspase-dependent and caspase-independent apoptosis.\",\n      \"method\": \"Cardiomyocyte-specific conditional CPNS1 knockout mice, in vitro ISC-REP, mitochondrial fractionation, proteomics (mass spectrometry), infarct size measurement, mitochondrial permeability transition assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic deletion with proteomics identifying substrate candidates and multiple functional mitochondrial readouts, single lab\",\n      \"pmids\": [\"34997008\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Transient blockade of electron transport with amobarbital (AMO) during ischemia prevented both cytosolic CPN1 activation (measured by spectrin cleavage) and mitochondrial CPN1 activation (measured by AIF truncation) during ISC-REP, establishing that the damaged electron transport chain is an upstream driver of CPN1 activation, likely via calcium overload and oxidative stress.\",\n      \"method\": \"Buffer-perfused rat heart ISC-REP, amobarbital ETC blockade, cytosol/mitochondria fractionation, spectrin cleavage and AIF truncation as CPN1 activity reporters\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological intervention with two orthogonal CPN1 activity readouts placing ETC upstream of CPN1 activation, single lab\",\n      \"pmids\": [\"35550199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In vitro incubation of a mitofilin peptide with exogenous CPN1 led to mitofilin degradation, establishing mitofilin as a direct CPN1 substrate. In DCD rat hearts, CPN1/2 inhibition with MDL-28170 preserved mitofilin expression, decreased mitochondrial permeability transition pore opening, and reduced infarct size, placing CPN1-mediated mitofilin cleavage upstream of MPTP opening.\",\n      \"method\": \"In vitro peptide cleavage assay with exogenous CPN1, DCD rat heart model, MDL-28170 inhibition, mitofilin Western blotting, MPTP assay, infarct size measurement\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro substrate cleavage reconstitution plus functional in vivo confirmation, single lab\",\n      \"pmids\": [\"42193929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CPN1 cleaves the C-terminal arginine from KNG1K438-R457 (a kininogen-1 peptide fragment). In BRCA1-mutant breast cancer, decreased CPN1 activity combined with increased KLK2 activity results in accumulation of KNG1K438-R457 in serum. This was established by assaying purified CPN1 with synthesized substrate peptides and validating cleavage in patient serum.\",\n      \"method\": \"In vitro enzymatic assay with purified CPN1 and synthesized substrate, patient serum validation, mass spectrometry\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic reconstitution with defined substrate, validated in patient samples, single lab\",\n      \"pmids\": [\"27058005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Three CPN1 gene variants (c.533G>A, c.582A>G, c.734C>T) in the catalytic 55-kDa subunit were identified in 4 unrelated families with hereditary angioedema and normal C1 inhibitor (HAE-nC1-INH). Affected patients had CPN plasma activity 30–50% of median. CPN deficiency segregated with HAE-nC1-INH symptoms, establishing that loss-of-function CPN1 variants contribute to bradykinin and anaphylatoxin accumulation causing angioedema.\",\n      \"method\": \"Next-generation sequencing, Sanger sequencing, CPN enzyme activity measurement in patient plasma, segregation analysis in families\",\n      \"journal\": \"The journal of allergy and clinical immunology. Global\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct sequencing with functional CPN activity measurement and familial segregation in 4 independent families\",\n      \"pmids\": [\"38445235\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CPN1 encodes the 50-kDa catalytic subunit of the plasma zinc metalloprotease carboxypeptidase N, which forms a heterotetrameric complex with two CPN2 regulatory subunits; the crystal structure reveals an active-site groove restricted by surface loops and a C-terminal transthyretin domain, with the enzyme cleaving C-terminal Lys/Arg residues from complement anaphylatoxins (C3a, C5a), kinins, and other vasoactive peptides to regulate inflammation, and whose loss-of-function—whether by gene knockout, rare coding variants, or reduced activity—causes hypersensitivity to C5a-mediated anaphylactic shock and hereditary angioedema; additionally, a mitochondria-localized pool of CPN1 is activated downstream of electron transport chain damage during ischemia-reperfusion, where it cleaves complex I subunit NDUFS7 and the inner membrane protein mitofilin to impair oxidative phosphorylation and trigger apoptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CPN1 encodes the 50-kDa catalytic subunit of carboxypeptidase N, a regulatory B-type zinc metalloprotease that cleaves C-terminal arginine and lysine residues from plasma peptides—including the complement anaphylatoxins C3a and C5a, kinins, and kininogen-derived fragments—thereby inactivating or modulating their receptor-binding activity to control inflammation and vascular tone [#2, #11]. Its crystal structure resolves an N-terminal catalytic domain joined to a C-terminal transthyretin β-sandwich domain; two surface loops restrict the active-site groove (explaining resistance to protein carboxypeptidase inhibitors), an S1' pocket favoring C-terminal Lys over Arg accounts for substrate preference, and a hydrophobic patch at the catalytic–transthyretin domain interface mediates assembly with the CPN2 regulatory subunit [#0]. In vivo, CPN1 enzymatic activity is required to inactivate C5a: knockout mice are hypersensitive to lethal, histamine-mediated anaphylactic shock that depends on C5a/C5aR rather than C3a/C3aR signaling [#1]. Loss-of-function CPN1 coding variants reduce plasma CPN activity and cause carboxypeptidase N deficiency and hereditary angioedema with normal C1 inhibitor, attributed to accumulation of bradykinin and anaphylatoxins [#4, #12]. Beyond its plasma role, a mitochondrial and cytosolic pool of CPN1 is activated downstream of electron transport chain damage during cardiac ischemia-reperfusion, where it cleaves the complex I subunit NDUFS7 and the inner-membrane protein mitofilin, impairs oxidative phosphorylation and mitophagy, promotes mitochondrial permeability transition pore opening, and triggers apoptosis [#7, #9, #10].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing the gene identity and genomic location of the carboxypeptidase N catalytic subunit was the prerequisite for any molecular dissection of the enzyme.\",\n      \"evidence\": \"PCR mapping on somatic cell hybrid DNA panel localizing CPN1 to chromosome 10\",\n      \"pmids\": [\"9628828\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional or structural characterization at this stage\", \"Subunit assembly with CPN2 not yet addressed\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Linking human carboxypeptidase N deficiency to CPN1 itself answered whether the enzymatic phenotype was attributable to the catalytic gene, identifying loss-of-function alleles including a mutation at a conserved active-site residue.\",\n      \"evidence\": \"Genomic sequencing of a biochemically confirmed deficient proband plus control allele-frequency analysis\",\n      \"pmids\": [\"12560874\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single proband; broader genotype-phenotype spectrum unresolved\", \"Functional consequence of G178D not directly tested by enzymology\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defining the enzyme's substrate spectrum established CPN as the plasma carboxypeptidase that inactivates anaphylatoxins, kinins, and vasoactive peptides by removing C-terminal basic residues.\",\n      \"evidence\": \"Synthesis of in vitro enzyme-activity data on C3a, C5a, and kinin cleavage\",\n      \"pmids\": [\"14687935\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative physiological contribution of individual substrates not ranked\", \"Does not establish which substrate dominates pathology in vivo\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Detecting CPN1 expression in early embryonic erythroid and hepatic cells before complement activation raised the possibility of a developmental role independent of its known anaphylatoxin-regulating function.\",\n      \"evidence\": \"In situ hybridization and protein detection across mouse embryonic stages\",\n      \"pmids\": [\"15177117\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No developmental phenotype demonstrated from this expression data\", \"Substrate or pathway in embryonic tissues not identified\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The crystal structure explained substrate selectivity and inhibitor resistance mechanistically and defined the surface that mediates CPN2 binding.\",\n      \"evidence\": \"2.1 Å X-ray structure of the catalytic domain with bradykinin active-site modeling\",\n      \"pmids\": [\"17157876\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the intact heterotetramer with CPN2 not determined\", \"Catalytic mechanism inferred from modeling rather than substrate-bound complexes\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Genetic epistasis in knockout mice resolved which anaphylatoxin drives the lethal phenotype, placing CPN1 activity upstream of C5a/C5aR-mediated histamine release rather than the C3a axis.\",\n      \"evidence\": \"CPN1 knockout mice with C5aR-/- and C3aR-/- double knockouts, cobra venom factor and i.v. anaphylatoxin challenge, antihistamine rescue\",\n      \"pmids\": [\"19414808\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Human relevance of mortality phenotype not directly tested\", \"Contribution of kinin substrates to phenotype not dissected\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identifying a specific kininogen-derived substrate and tying reduced CPN1 activity to a disease serum biomarker extended the enzyme's relevance beyond classical anaphylatoxin control.\",\n      \"evidence\": \"In vitro cleavage of KNG1K438-R457 by purified CPN1 with patient-serum validation and mass spectrometry\",\n      \"pmids\": [\"27058005\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal role of CPN1 activity change in BRCA1-mutant cancer not established\", \"Single lab; mechanism of activity reduction unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Discovery that a mitochondrial CPN1 pool cleaves complex I subunit NDUFS7 during ischemia-reperfusion introduced an intracellular proteolytic function distinct from the plasma metalloprotease role.\",\n      \"evidence\": \"Rat heart ISC-REP model with MDL-28170 inhibition, mitochondrial fractionation, complex I activity assays, and NDUFS7/beclin-1 Western blotting\",\n      \"pmids\": [\"31411917\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"NDUFS7 cleavage shown functionally but not by direct in vitro reconstitution\", \"Relationship between this calpain-like activity and the plasma carboxypeptidase function not reconciled\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Cardiomyocyte CPNS1 deletion and upstream ETC blockade together established that electron transport chain damage drives CPN1 activation and that CPN1/2 cleaves additional mitochondrial targets to impair OXPHOS and trigger apoptosis.\",\n      \"evidence\": \"Conditional CPNS1 knockout mice with proteomics, infarct sizing and MPTP assays; amobarbital ETC blockade with spectrin-cleavage and AIF-truncation activity reporters\",\n      \"pmids\": [\"34997008\", \"35550199\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Proteomic targets (paraplegin, sarcalumenin, complex III) identified as candidates without direct cleavage reconstitution\", \"Single lab; human cardiac relevance not established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Familial CPN1 variants causing hereditary angioedema with normal C1 inhibitor confirmed that reduced CPN activity drives bradykinin/anaphylatoxin accumulation and human disease.\",\n      \"evidence\": \"NGS/Sanger sequencing of four families, plasma CPN activity measurement, and segregation analysis\",\n      \"pmids\": [\"38445235\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional impact of each variant on enzyme structure not biochemically resolved\", \"Why partial (30-50%) activity loss produces symptoms not mechanistically explained\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Direct in vitro cleavage of mitofilin by CPN1, with in vivo correlation to MPTP opening, identified mitofilin as a direct substrate and positioned CPN1 proteolysis upstream of permeability transition in ischemic injury.\",\n      \"evidence\": \"In vitro mitofilin peptide cleavage with exogenous CPN1 plus DCD rat heart model with MDL-28170 inhibition, mitofilin Western blotting, MPTP and infarct assays\",\n      \"pmids\": [\"42193929\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; human cardiac data absent\", \"Molecular link between mitofilin loss and MPTP opening not fully resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the secreted plasma carboxypeptidase activity and the intracellular ischemia-activated proteolytic activity attributed to CPN1 are mechanistically related, and whether they reflect the same protein, distinct pools, or a nomenclature overlap.\",\n      \"evidence\": \"No reconciling experiment in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No study directly connects the plasma metalloprotease and mitochondrial activities\", \"Structural basis of the intracellular activity is uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 7, 10, 11]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 2, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2, 12]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [7, 9, 10]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [7, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [8, 10]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 12]}\n    ],\n    \"complexes\": [\"Carboxypeptidase N heterotetramer (CPN1/CPN2)\"],\n    \"partners\": [\"CPN2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}