{"id":"ec99394c-e48d-502d-85c9-34dc972da6ff","stable_key":"a9dd23c6-978a-5755-8bd8-f29bd1fe0cda:b3-pre-naprt-reaction","predicate":"catalyzes-production-of","statement":"Human NAPRT catalyzes phosphoribosyl transfer from PRPP to nicotinic acid, producing nicotinic acid mononucleotide and pyrophosphate.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"80418b83-e480-5422-a1d6-33a115362932","mechanism_event_label":"Nicotinic acid enters its NAD-building route through NAPRT.","subject":{"id":"ee8024b9-b9e9-513f-9bcd-b3d30e1990ba","slug":"naprt","display_name":"Human nicotinate phosphoribosyltransferase / NAPRT","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":"80418b83-e480-5422-a1d6-33a115362932","stable_key":"a9dd23c6-978a-5755-8bd8-f29bd1fe0cda:b3-pre-naprt-reaction-event","event_type":"biochemical_relationship","label":"Nicotinic acid enters its NAD-building route through NAPRT.","description":"Human NAPRT catalyzes phosphoribosyl transfer from PRPP to nicotinic acid, producing nicotinic acid mononucleotide and pyrophosphate.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"ee8024b9-b9e9-513f-9bcd-b3d30e1990ba","slug":"naprt","display_name":"Human nicotinate phosphoribosyltransferase / NAPRT","entity_type_key":"protein"},"role":"enzyme","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"9751fdb6-9b30-586f-b07a-79b8e2cd62dd","slug":"nicotinic-acid","display_name":"Nicotinic 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":"phosphoribosyl donor","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/naprt2015.abstract.txt\", \"locator\": \"Indexed primary abstract\", \"start_char\": 0, \"end_char\": 1606, \"file_sha256\": \"df6e36cf3464d4cda171d06ee24065532dee0d8b5fd5c3ccafcb1cc8df951bbe\", \"text_sha256\": \"df6e36cf3464d4cda171d06ee24065532dee0d8b5fd5c3ccafcb1cc8df951bbe\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Recombinant human NAPRT crystallography and docking; purified protein, no intact tissue","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":"Purified-enzyme evidence does not establish dietary intake requirements or clinical outcomes.","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":"Nicotinic acid enters its NAD-building route through NAPRT.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[b3-pre-naprt2015] Crystal structure of human nicotinic acid phosphoribosyltransferase. (2015). https://pubmed.ncbi.nlm.nih.gov/26042198/ DOI: 10.1016/j.fob.2015.05.002","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified recombinant protein; no intact tissue","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"94db2e6c-2dd9-5557-8e54-5f272ae44e11","evidence_kind":"source_excerpt","locator":"Lines 249-260","start_line":249,"end_line":260,"excerpt":"### b3-pre-naprt-reaction\nHuman NAPRT catalyzes phosphoribosyl transfer from PRPP to nicotinic acid, producing nicotinic acid mononucleotide and pyrophosphate.\nCondition category: normal\nnutrient_topic: Niacin research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Nicotinic acid enters its NAD-building route through NAPRT.\norganism: Homo sapiens\ntissue_or_cell_type: Purified recombinant protein; no intact tissue\nexperimental_model: Recombinant human NAPRT crystallography and docking; purified protein, no intact tissue\nlimitations: Purified-enzyme evidence does not establish dietary intake requirements or clinical outcomes.\nexposure: Biochemical or structural assay; no dietary intervention\nevidence_span: {\"source_cache\": \"artifacts/niacin-precursors-sources/naprt2015.abstract.txt\", \"locator\": \"Indexed primary abstract\", \"start_char\": 0, \"end_char\": 1606, \"file_sha256\": \"df6e36cf3464d4cda171d06ee24065532dee0d8b5fd5c3ccafcb1cc8df951bbe\", \"text_sha256\": \"df6e36cf3464d4cda171d06ee24065532dee0d8b5fd5c3ccafcb1cc8df951bbe\"}\n[b3-pre-naprt2015] Crystal structure of human nicotinic acid phosphoribosyltransferase. (2015). https://pubmed.ncbi.nlm.nih.gov/26042198/ DOI: 10.1016/j.fob.2015.05.002","model_system":"Recombinant human NAPRT crystallography and docking; purified protein, no intact tissue","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [b3-pre-naprt2015] Crystal structure of human nicotinic acid phosphoribosyltransferase. (2015). https://pubmed.ncbi.nlm.nih.gov/26042198/ DOI: 10.1016/j.fob.2015.05.002","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"a62b7b5b-786a-57e9-85e9-67c6912a5054","stable_key":"import-a9dd23c6-978a-5755-8bd8-f29bd1fe0cda","title":"Niacin: NAD metabolism, 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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