{"id":"b169d691-26ce-5998-96b1-fc09cfb7ac2f","stable_key":"56f1d914-e7da-595a-af69-c217b2b47407:l-phenylalanine-qdpr-nadh","predicate":"binds","statement":"A catalytically characterized recombinant human dihydropteridine reductase was crystallized in complex with NADH at 2.5-angstrom resolution.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"7fbb1b64-8026-5a38-83ce-2b191ba8d5bd","mechanism_event_label":"The cofactor-recycling network includes an NADH-binding enzyme.","subject":{"id":"d255add1-af3d-5e6c-8d5e-b87c3248a7c5","slug":"qdpr","display_name":"Human quinoid dihydropteridine reductase / QDPR","entity_type_key":"protein"},"object":{"id":"9fbf2e03-16a9-5ca7-965c-0bfc07ca24da","slug":"nadh","display_name":"NADH","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"7fbb1b64-8026-5a38-83ce-2b191ba8d5bd","stable_key":"56f1d914-e7da-595a-af69-c217b2b47407:l-phenylalanine-qdpr-nadh-event","event_type":"observed_relationship","label":"The cofactor-recycling network includes an NADH-binding enzyme.","description":"A catalytically characterized recombinant human dihydropteridine reductase was crystallized in complex with NADH at 2.5-angstrom resolution.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"d255add1-af3d-5e6c-8d5e-b87c3248a7c5","slug":"qdpr","display_name":"Human quinoid dihydropteridine reductase / QDPR","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"9fbf2e03-16a9-5ca7-965c-0bfc07ca24da","slug":"nadh","display_name":"NADH","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"190407ad-0219-54b5-b05f-7c75f3895ca6","slug":"l-phenylalanine","display_name":"L-Phenylalanine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"1c231b90-c106-507a-8766-870ecb40e368","slug":"tetrahydrobiopterin","display_name":"Tetrahydrobiopterin / BH4","entity_type_key":"small_molecule"},"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":"Human QDPR expressed in E. coli; enzyme purification, kinetic characterization and structure.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This binary structure alone does not show that niacin supplementation changes phenylalanine clearance.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Phenylalanine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-phenylalanine","display_name":"L-Phenylalanine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"The cofactor-recycling network includes an NADH-binding enzyme.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"The crystallographic structure of a human dihydropteridine reductase NADH binary complex expressed in Escherichia coli by a cDNA constructed from its rat homologue. · 1993 · https://pubmed.ncbi.nlm.nih.gov/8262916/","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"24f3170e-a65a-5df4-a6c1-38f46866d1e4","evidence_kind":"source_excerpt","locator":"Lines 70-76","start_line":70,"end_line":76,"excerpt":"## l-phenylalanine-qdpr-nadh\nThe cofactor-recycling network includes an NADH-binding enzyme.\nA catalytically characterized recombinant human dihydropteridine reductase was crystallized in complex with NADH at 2.5-angstrom resolution.\nModel: Human QDPR expressed in E. coli; enzyme purification, kinetic characterization and structure.\nLimitations: This binary structure alone does not show that niacin supplementation changes phenylalanine clearance.\nEvidence access: Primary abstract\nThe crystallographic structure of a human dihydropteridine reductase NADH binary complex expressed in Escherichia coli by a cDNA constructed from its rat homologue. · 1993 · https://pubmed.ncbi.nlm.nih.gov/8262916/","model_system":"Human QDPR expressed in E. coli; enzyme purification, kinetic characterization and structure.","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":"54de7c56-1e60-5d7b-8ef9-852c58ae92ba","stable_key":"import-56f1d914-e7da-595a-af69-c217b2b47407","title":"L-Phenylalanine: transport, protein synthesis, cofactor recycling 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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