{"id":"62827040-17dd-5974-a010-77f02bc62b08","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-pnp-product-inhibition","predicate":"inhibits","statement":"PLP competitively inhibited purified human PNPO in the reported kinetic assays.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"negative","is_public":true,"mechanism_event_id":"ce2f2b39-a8eb-5b49-9007-1af151fafe41","mechanism_event_label":"The active B6 product can slow its own formation in vitro.","subject":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"object":{"id":"a01d08b9-a749-5bc3-934b-af0b35024b54","slug":"pnpo","display_name":"Pyridoxine 5-prime-phosphate oxidase / PNPO","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"ce2f2b39-a8eb-5b49-9007-1af151fafe41","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-pnp-product-inhibition-event","event_type":"biochemical_relationship","label":"The active B6 product can slow its own formation in vitro.","description":"PLP competitively inhibited purified human PNPO in the reported kinetic assays.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"role":"product inhibitor","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"a01d08b9-a749-5bc3-934b-af0b35024b54","slug":"pnpo","display_name":"Pyridoxine 5-prime-phosphate oxidase / PNPO","entity_type_key":"protein"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"B6-product feedback regulates a B2-dependent enzyme.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Results: kinetic properties; Table 1; FMN-binding structure","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Recombinant human PNPO expressed in E. coli; crystallography and purified-enzyme kinetics at 37 C.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Purified-enzyme assay","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"The paper did not establish free PLP pools or inhibition magnitude in intact mammalian tissues.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Riboflavin research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"riboflavin","display_name":"Riboflavin (vitamin B2)","entity_type_key":"small_molecule"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"The active B6 product can slow its own formation in vitro.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[musayev2003] Structure and properties of recombinant human pyridoxine 5'-phosphate oxidase. (2003). https://pubmed.ncbi.nlm.nih.gov/12824491/ DOI: 10.1110/ps.0356203","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified recombinant enzyme; no intact tissue","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"a0c6ba0f-7044-5319-9a4f-65f86529f4a1","evidence_kind":"source_excerpt","locator":"Lines 1178-1190","start_line":1178,"end_line":1190,"excerpt":"### b2-pnp-product-inhibition\nPLP competitively inhibited purified human PNPO in the reported kinetic assays.\nCondition category: normal\nnutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: The active B6 product can slow its own formation in vitro.\norganism: Homo sapiens\ntissue_or_cell_type: Purified recombinant enzyme; no intact tissue\nexperimental_model: Recombinant human PNPO expressed in E. coli; crystallography and purified-enzyme kinetics at 37 C.\nlimitations: The paper did not establish free PLP pools or inhibition magnitude in intact mammalian tissues.\nexposure: Purified-enzyme assay\ncross_nutrient: B6-product feedback regulates a B2-dependent enzyme.\nevidence_location: Results: kinetic properties; Table 1; FMN-binding structure\n[musayev2003] Structure and properties of recombinant human pyridoxine 5'-phosphate oxidase. (2003). https://pubmed.ncbi.nlm.nih.gov/12824491/ DOI: 10.1110/ps.0356203","model_system":"Recombinant human PNPO expressed in E. coli; crystallography and purified-enzyme kinetics at 37 C.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [musayev2003] Structure and properties of recombinant human pyridoxine 5'-phosphate oxidase. (2003). https://pubmed.ncbi.nlm.nih.gov/12824491/ DOI: 10.1110/ps.0356203","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"4f7c9578-82bf-5e2d-b5c4-72a79fb4f6af","stable_key":"import-548ab9d6-3a9b-5bed-879c-17d03813b636","title":"Riboflavin: 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. 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