{"id":"c4f43ef3-f2d7-5f83-b5d7-f202d25c795a","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-pnpo-r229w-fmn-affinity","predicate":"weakens-binding-of","statement":"R229W PNPO had an FMN dissociation constant approximately 50-fold higher than wild type in apoenzyme fluorescence titrations.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"negative","is_public":true,"mechanism_event_id":"038449f4-ad65-5385-8920-15423ae63e26","mechanism_event_label":"The genetic substitution weakens FMN binding.","subject":{"id":"aabc2b32-1160-59ea-af19-1f01761d6a9b","slug":"pnpo-r229w","display_name":"PNPO Arg229Trp protein","entity_type_key":"protein_state"},"object":{"id":"d3eacf85-1a35-546d-bd30-161474dd9691","slug":"fmn","display_name":"Flavin mononucleotide","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"038449f4-ad65-5385-8920-15423ae63e26","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-pnpo-r229w-fmn-affinity-event","event_type":"biochemical_relationship","label":"The genetic substitution weakens FMN binding.","description":"R229W PNPO had an FMN dissociation constant approximately 50-fold higher than wild type in apoenzyme fluorescence titrations.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"d3eacf85-1a35-546d-bd30-161474dd9691","slug":"fmn","display_name":"Flavin mononucleotide","entity_type_key":"small_molecule"},"role":"titrated cofactor","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":"wild-type comparator","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"aabc2b32-1160-59ea-af19-1f01761d6a9b","slug":"pnpo-r229w","display_name":"PNPO Arg229Trp protein","entity_type_key":"protein_state"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"availability_state","value_text":"machinery_impairment","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null},{"dimension":"cross_nutrient","value_text":"A B6-activation disorder directly disrupts B2-cofactor binding.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Results: Table 3 and Fig 1; Table 2 and Fig 2","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Recombinant human wild-type and R229W PNPO; fluorescence titration, kinetics and 2.5-A mutant structure.","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":"Biochemical evidence does not establish a dietary threshold or supplementation benefit.","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 genetic substitution weakens FMN binding.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[musayev2009] Molecular basis of reduced pyridoxine 5'-phosphate oxidase catalytic activity in neonatal epileptic encephalopathy disorder. (2009). https://pubmed.ncbi.nlm.nih.gov/19759001/ DOI: 10.1074/jbc.m109.038372","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},{"dimension":"trigger_kind","value_text":"machinery_impairment","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null}],"evidence":[{"id":"7b074e82-38cf-51f0-8d1c-93b35353b06a","evidence_kind":"source_excerpt","locator":"Lines 1206-1218","start_line":1206,"end_line":1218,"excerpt":"### b2-pnpo-r229w-fmn-affinity\nR229W PNPO had an FMN dissociation constant approximately 50-fold higher than wild type in apoenzyme fluorescence titrations.\nCondition category: machinery_impairment\nnutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: The genetic substitution weakens FMN binding.\norganism: Homo sapiens\ntissue_or_cell_type: Purified recombinant enzyme; no intact tissue\nexperimental_model: Recombinant human wild-type and R229W PNPO; fluorescence titration, kinetics and 2.5-A mutant structure.\nlimitations: Biochemical evidence does not establish a dietary threshold or supplementation benefit.\nexposure: Purified-enzyme assay\ncross_nutrient: A B6-activation disorder directly disrupts B2-cofactor binding.\nevidence_location: Results: Table 3 and Fig 1; Table 2 and Fig 2\n[musayev2009] Molecular basis of reduced pyridoxine 5'-phosphate oxidase catalytic activity in neonatal epileptic encephalopathy disorder. 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