{"id":"3e6332c6-5143-5bb7-8bb9-b1cbd4e8a62b","stable_key":"97957230-601f-5dec-8524-0812be8fadbf:l-threonine-human-sds-plp","predicate":"supports","statement":"Deleting Pro128 from human hepatic SDS changed substrate kinetic constants and affinity for pyridoxal phosphate.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"0d1ee286-aaf4-5c08-9852-1f21aebd6fe2","mechanism_event_label":"B6-dependent chemistry also depends on the enzyme structure that binds its cofactor.","subject":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"object":{"id":"fc4df87c-aec1-5de5-8122-effc2c5ee721","slug":"sds","display_name":"Human hepatic serine dehydratase / SDS","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"0d1ee286-aaf4-5c08-9852-1f21aebd6fe2","stable_key":"97957230-601f-5dec-8524-0812be8fadbf:l-threonine-human-sds-plp-event","event_type":"observed_relationship","label":"B6-dependent chemistry also depends on the enzyme structure that binds its cofactor.","description":"Deleting Pro128 from human hepatic SDS changed substrate kinetic constants and affinity for pyridoxal phosphate.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"fc4df87c-aec1-5de5-8122-effc2c5ee721","slug":"sds","display_name":"Human hepatic serine dehydratase / SDS","entity_type_key":"protein"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"fcef4dc2-a7b6-5812-bc33-c8af3d83f4d0","slug":"l-threonine","display_name":"L-Threonine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"694036f6-b7f5-5bc0-8967-a4de835ba23c","slug":"sdsl","display_name":"Human serine dehydratase-like protein / SDSL","entity_type_key":"protein"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified wild-type and engineered human enzymes.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This manipulation does not show that additional B6 restores a mutant enzyme or that ordinary dietary B6 is limiting.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Threonine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-threonine","display_name":"L-Threonine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"B6-dependent chemistry also depends on the enzyme structure that binds its cofactor.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Enzymatic and biochemical properties of a novel human serine dehydratase isoform. · 2006 · https://pubmed.ncbi.nlm.nih.gov/16580895/ · DOI 10.1016/j.bbapap.2006.02.010","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"65643dcf-65b9-5421-995b-668b10015992","evidence_kind":"source_excerpt","locator":"Lines 266-272","start_line":266,"end_line":272,"excerpt":"## l-threonine-human-sds-plp\nB6-dependent chemistry also depends on the enzyme structure that binds its cofactor.\nDeleting Pro128 from human hepatic SDS changed substrate kinetic constants and affinity for pyridoxal phosphate.\nModel: Purified wild-type and engineered human enzymes.\nLimitations: This manipulation does not show that additional B6 restores a mutant enzyme or that ordinary dietary B6 is limiting.\nEvidence access: Primary abstract\nEnzymatic and biochemical properties of a novel human serine dehydratase isoform. · 2006 · https://pubmed.ncbi.nlm.nih.gov/16580895/ · DOI 10.1016/j.bbapap.2006.02.010","model_system":"Purified wild-type and engineered human enzymes.","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":"35396730-235a-537e-8a05-c6ef2960c509","stable_key":"import-97957230-601f-5dec-8524-0812be8fadbf","title":"L-Threonine: translation, intestinal barrier, metabolism 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. 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