{"id":"ae840364-c220-5ac6-909d-97b1dafbb167","stable_key":"a8baf7e9-80e4-5d8c-adec-9a63e84d2f21:l-cysteine-mpst-sulfur-transfer","predicate":"transfers_sulfur_from","statement":"Human MPST transfers sulfur from 3-mercaptopyruvate to its active-site Cys248, releasing pyruvate and forming an enzyme-bound persulfide.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"a599b1be-0ceb-545a-9516-bd09b02716f7","mechanism_event_label":"A cysteine-derived intermediate hands sulfur to an enzyme before it reaches another acceptor.","subject":{"id":"bd69cbdf-a220-5981-b89f-c31b53f25f40","slug":"mpst","display_name":"Human mercaptopyruvate sulfurtransferase / MPST","entity_type_key":"protein"},"object":{"id":"fd727c98-d9db-5c94-9fc3-8f7c6f8272df","slug":"3-mercaptopyruvate","display_name":"3-Mercaptopyruvate","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"a599b1be-0ceb-545a-9516-bd09b02716f7","stable_key":"a8baf7e9-80e4-5d8c-adec-9a63e84d2f21:l-cysteine-mpst-sulfur-transfer-event","event_type":"observed_relationship","label":"A cysteine-derived intermediate hands sulfur to an enzyme before it reaches another acceptor.","description":"Human MPST transfers sulfur from 3-mercaptopyruvate to its active-site Cys248, releasing pyruvate and forming an enzyme-bound persulfide.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"bd69cbdf-a220-5981-b89f-c31b53f25f40","slug":"mpst","display_name":"Human mercaptopyruvate sulfurtransferase / MPST","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"fd727c98-d9db-5c94-9fc3-8f7c6f8272df","slug":"3-mercaptopyruvate","display_name":"3-Mercaptopyruvate","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"ca899f13-50ad-55e5-ab99-329ae0038c74","slug":"l-cysteine","display_name":"L-Cysteine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"b08835d2-3c24-52dd-b9b9-a1d34c28b14f","slug":"human-mpst-enzyme-persulfide","display_name":"Human MPST active-site cysteine persulfide","entity_type_key":"cellular_process"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"91e6d4f5-fba1-542d-b68a-57cc28e1e425","slug":"pyruvate","display_name":"Pyruvate","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract and primary figure descriptions","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified human MPST structure and kinetics at pH 7.4.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"The upstream cysteine transamination is pathway context; this experiment does not identify its dominant human tissue isoenzyme.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Cysteine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-cysteine","display_name":"L-Cysteine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"A cysteine-derived intermediate hands sulfur to an enzyme before it reaches another acceptor.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Structure and kinetic analysis of H2S production by human mercaptopyruvate sulfurtransferase. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23698001/ · DOI 10.1074/jbc.M113.466177","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"03e713b6-9ab5-5ed3-98d8-bbf66b4c764e","evidence_kind":"source_excerpt","locator":"Lines 452-458","start_line":452,"end_line":458,"excerpt":"## l-cysteine-mpst-sulfur-transfer\nA cysteine-derived intermediate hands sulfur to an enzyme before it reaches another acceptor.\nHuman MPST transfers sulfur from 3-mercaptopyruvate to its active-site Cys248, releasing pyruvate and forming an enzyme-bound persulfide.\nModel: Purified human MPST structure and kinetics at pH 7.4.\nLimitations: The upstream cysteine transamination is pathway context; this experiment does not identify its dominant human tissue isoenzyme.\nEvidence access: Primary abstract and primary figure descriptions\nStructure and kinetic analysis of H2S production by human mercaptopyruvate sulfurtransferase. · 2013 · https://pubmed.ncbi.nlm.nih.gov/23698001/ · DOI 10.1074/jbc.M113.466177","model_system":"Purified human MPST structure and kinetics at pH 7.4.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access and experimental limitations specified.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"654560f6-8d7f-596b-8722-48d94053cfe3","stable_key":"import-a8baf7e9-80e4-5d8c-adec-9a63e84d2f21","title":"L-Cysteine: sulfur allocation, redox supply and cross-nutrient mechanisms (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text.","file_path":"","sha256":"f722669e54eab08ffe7289f9d79ddfc443014ed8c4bc5ba10ce2635470d22498","revision_id":"8ae25609-a031-5782-9c62-6cad8767ea46","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}