{"id":"eb1fc380-3d67-532d-ab3e-19a44dcbdca2","stable_key":"1310afbd-6010-586e-805d-551d846da421:b6-met-cth-cleavage","predicate":"catalyzes-conversion-of","statement":"Human CTH cleaves cystathionine to cysteine, 2-oxobutanoate and ammonia in a PLP-dependent reaction.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"81dc19a1-dbe3-5808-aaa3-847b4c3f5176","mechanism_event_label":"This step releases cysteine for downstream metabolism.","subject":{"id":"4014ee3a-0e44-5379-b541-174aa75bcf90","slug":"cth","display_name":"Human cystathionine gamma-lyase / CTH","entity_type_key":"protein"},"object":{"id":"ffc7d833-38ce-5224-82e0-19c0b87b45bf","slug":"cystathionine","display_name":"Cystathionine","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"81dc19a1-dbe3-5808-aaa3-847b4c3f5176","stable_key":"1310afbd-6010-586e-805d-551d846da421:b6-met-cth-cleavage-event","event_type":"biochemical_relationship","label":"This step releases cysteine for downstream metabolism.","description":"Human CTH cleaves cystathionine to cysteine, 2-oxobutanoate and ammonia in a PLP-dependent reaction.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"4014ee3a-0e44-5379-b541-174aa75bcf90","slug":"cth","display_name":"Human cystathionine gamma-lyase / CTH","entity_type_key":"protein"},"role":"enzyme","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"role":"cofactor","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"ffc7d833-38ce-5224-82e0-19c0b87b45bf","slug":"cystathionine","display_name":"Cystathionine","entity_type_key":"small_molecule"},"role":"substrate","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"ca899f13-50ad-55e5-ab99-329ae0038c74","slug":"l-cysteine","display_name":"L-Cysteine","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"1eb0252c-ddf6-54ff-a9cd-b8c820769ba7","slug":"2-oxobutanoate","display_name":"2-Oxobutanoate / alpha-ketobutyrate","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""},{"entity":{"id":"1374ec24-1a5b-552b-982f-51f9082f4187","slug":"ammonia","display_name":"Ammonia","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":5,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"B6-dependent sulfur transfer supplies cysteine; glutathione synthesis requires additional enzymes.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified human CTH apo/holo crystal structures and assays","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Purified-enzyme evidence does not define dietary requirements or cellular PLP thresholds.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-b6","display_name":"Vitamin B6","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"This step releases cysteine for downstream metabolism.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[b6-cth-structure-2009] Structural Basis for the Inhibition Mechanism of Human Cystathionine gamma-Lyase, an Enzyme Responsible for the Production of H2S (2009). https://doi.org/10.1074/jbc.M805459200 DOI: 10.1074/jbc.M805459200","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified recombinant protein; no intact tissue","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"880a16ad-5a76-52ad-bacb-7711ffcca8d6","evidence_kind":"source_excerpt","locator":"Lines 554-564","start_line":554,"end_line":564,"excerpt":"### b6-met-cth-cleavage\nHuman CTH cleaves cystathionine to cysteine, 2-oxobutanoate and ammonia in a PLP-dependent reaction.\nCondition category: normal\nnutrient_topic: Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: This step releases cysteine for downstream metabolism.\norganism: Homo sapiens\ntissue_or_cell_type: Purified recombinant protein; no intact tissue\nexperimental_model: Purified human CTH apo/holo crystal structures and assays\nlimitations: Purified-enzyme evidence does not define dietary requirements or cellular PLP thresholds.\ncross_nutrient: B6-dependent sulfur transfer supplies cysteine; glutathione synthesis requires additional enzymes.\n[b6-cth-structure-2009] Structural Basis for the Inhibition Mechanism of Human Cystathionine gamma-Lyase, an Enzyme Responsible for the Production of H2S (2009). https://doi.org/10.1074/jbc.M805459200 DOI: 10.1074/jbc.M805459200","model_system":"Purified human CTH apo/holo crystal structures and assays","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [b6-cth-structure-2009] Structural Basis for the Inhibition Mechanism of Human Cystathionine gamma-Lyase, an Enzyme Responsible for the Production of H2S (2009). https://doi.org/10.1074/jbc.M805459200 DOI: 10.1074/jbc.M805459200","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"251773bb-16f5-5903-b135-db4a61d9dec4","stable_key":"import-1310afbd-6010-586e-805d-551d846da421","title":"Vitamin B6: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"ef0019b344b2219220f801a84d0d138ff6880c1be1a59540d9034bfa4334f61e","revision_id":"cac3555f-48af-5c52-a84e-add4482c87fb","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}