{"id":"2da1eb35-badd-56b8-a678-c2c3633eb5aa","stable_key":"a9dd23c6-978a-5755-8bd8-f29bd1fe0cda:b3-pre-qprt-namn","predicate":"catalyzes-production-of","statement":"Human QPRT converts quinolinate and PRPP toward nicotinic acid mononucleotide; the human enzyme structures resolve reactant quinolinate and product NaMN complexes.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"78caac89-2427-576d-bee9-4793981de507","mechanism_event_label":"Quinolinate enters the same deamidated mononucleotide route used by nicotinic acid.","subject":{"id":"d4af739e-5f99-53c1-894c-c71f4e34c753","slug":"qprt","display_name":"Human quinolinate phosphoribosyltransferase / QPRT","entity_type_key":"protein"},"object":{"id":"a17c536e-82bd-5613-8114-79bb35ec8039","slug":"nicotinic-acid-mononucleotide","display_name":"Nicotinic acid mononucleotide","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"78caac89-2427-576d-bee9-4793981de507","stable_key":"a9dd23c6-978a-5755-8bd8-f29bd1fe0cda:b3-pre-qprt-namn-event","event_type":"biochemical_relationship","label":"Quinolinate enters the same deamidated mononucleotide route used by nicotinic acid.","description":"Human QPRT converts quinolinate and PRPP toward nicotinic acid mononucleotide; the human enzyme structures resolve reactant quinolinate and product NaMN complexes.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"d4af739e-5f99-53c1-894c-c71f4e34c753","slug":"qprt","display_name":"Human quinolinate phosphoribosyltransferase / QPRT","entity_type_key":"protein"},"role":"enzyme","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ab444b3c-c8ec-5ada-8450-36ac9934d6b6","slug":"quinolinic-acid","display_name":"Quinolinic acid","entity_type_key":"small_molecule"},"role":"substrate","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"463bf8ac-c5d0-543d-a440-0070a62083e0","slug":"phosphoribosyl-pyrophosphate","display_name":"5-Phosphoribosyl 1-pyrophosphate","entity_type_key":"small_molecule"},"role":"substrate","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"a17c536e-82bd-5613-8114-79bb35ec8039","slug":"nicotinic-acid-mononucleotide","display_name":"Nicotinic acid mononucleotide","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"cd026fef-529f-5e03-b6b5-37ede8ce9127","slug":"pyrophosphate","display_name":"Inorganic pyrophosphate","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"evidence_span","value_text":"{\"source_cache\": \"artifacts/niacin-precursors-sources/qprt2016.paragraphs.txt\", \"locator\": \"Normalized full-text paragraphs 13–15 (0-based)\", \"start_char\": 10597, \"end_char\": 15612, \"file_sha256\": \"85fcc4a79a17f4f3846301f67698a444c3c9930829e167d86a96adbb72d830e6\", \"text_sha256\": \"8da78d25a53af6507018eece4ce553705dc505d0b169f678affad49ee21b10f6\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified recombinant human QPRT crystallography, calorimetry and oligomer studies","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Biochemical or structural assay; no dietary intervention","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Structural and biochemical enzyme study; does not establish how much dietary tryptophan becomes NAD in a person.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Niacin research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"niacin","display_name":"Niacin (vitamin B3)","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Quinolinate enters the same deamidated mononucleotide route used by nicotinic acid.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[b3-pre-qprt2016] Structural Insights into the Quaternary Catalytic Mechanism of Hexameric Human Quinolinate Phosphoribosyltransferase, a Key Enzyme in de novo NAD Biosynthesis. 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