{"id":"a60caabe-a7ce-5725-aaa8-04a1962c0df2","stable_key":"a8baf7e9-80e4-5d8c-adec-9a63e84d2f21:l-cysteine-cbs-h2s-branch","predicate":"produces_h2s_from","statement":"Purified human CBS favored H2S production through replacement of cysteine by homocysteine over the tested alternative cysteine reactions.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"476244f9-79b0-5883-a60a-3420cd68c9fc","mechanism_event_label":"An enzyme that helps synthesize cysteine can also use it in sulfur-gas production.","subject":{"id":"4688e32c-d7b6-5fca-9eb2-23307c29ae07","slug":"cbs","display_name":"Human cystathionine beta-synthase / CBS","entity_type_key":"protein"},"object":{"id":"ca899f13-50ad-55e5-ab99-329ae0038c74","slug":"l-cysteine","display_name":"L-Cysteine","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"476244f9-79b0-5883-a60a-3420cd68c9fc","stable_key":"a8baf7e9-80e4-5d8c-adec-9a63e84d2f21:l-cysteine-cbs-h2s-branch-event","event_type":"observed_relationship","label":"An enzyme that helps synthesize cysteine can also use it in sulfur-gas production.","description":"Purified human CBS favored H2S production through replacement of cysteine by homocysteine over the tested alternative cysteine reactions.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"4688e32c-d7b6-5fca-9eb2-23307c29ae07","slug":"cbs","display_name":"Human cystathionine beta-synthase / CBS","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ca899f13-50ad-55e5-ab99-329ae0038c74","slug":"l-cysteine","display_name":"L-Cysteine","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"70cc3ced-8adc-5e76-9750-e1415683455b","slug":"hydrogen-sulfide","display_name":"Hydrogen sulfide / H2S","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"5b635b42-bc0d-5c54-aa94-9cf76cd0ed47","slug":"homocysteine","display_name":"Homocysteine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human and yeast CBS kinetics, with human enzyme kept as this record’s subject.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Relative pathway dominance in a tissue cannot be read directly from purified-enzyme substrate tests.","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":"An enzyme that helps synthesize cysteine can also use it in sulfur-gas production.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Relative contributions of cystathionine beta-synthase and gamma-cystathionase to H2S biogenesis via alternative trans-sulfuration reactions. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19531479/ · DOI 10.1074/jbc.M109.010868","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"b7d19d2c-2f60-5ed8-80b8-97b6cedfdb3e","evidence_kind":"source_excerpt","locator":"Lines 284-290","start_line":284,"end_line":290,"excerpt":"## l-cysteine-cbs-h2s-branch\nAn enzyme that helps synthesize cysteine can also use it in sulfur-gas production.\nPurified human CBS favored H2S production through replacement of cysteine by homocysteine over the tested alternative cysteine reactions.\nModel: Human and yeast CBS kinetics, with human enzyme kept as this record’s subject.\nLimitations: Relative pathway dominance in a tissue cannot be read directly from purified-enzyme substrate tests.\nEvidence access: Primary abstract\nRelative contributions of cystathionine beta-synthase and gamma-cystathionase to H2S biogenesis via alternative trans-sulfuration reactions. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19531479/ · DOI 10.1074/jbc.M109.010868","model_system":"Human and yeast CBS kinetics, with human enzyme kept as this record’s subject.","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}