Pathway Human Homo sapiens

Nicotinate metabolism

R-HSA-196807 in Reactome release 97: under Metabolism of water-soluble vitamins and cofactors, with 29 genes placed in it by the mapping files and 0 child pathways in the hierarchy.

The same number in the other species

Reactome writes the mouse and rat events it infers from a human pathway under the human number with the species token. A door opens only where that species' own list in this release holds the id: R-MMU-196807 (mouse), R-RNO-196807 (rat). Whether the event was inferred from this one is what the record says.

The record
The genes
Parents and children

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This page reads the pathway's record from its source while you read the rest; with scripts off the card stays at its loading line. Reload with scripts on to see it, or open the source's own page from the link in the card.

01The record

Reactome's own record of this pathway

What this tells you

The pathway list, the hierarchy and the genes on this page are read from the files Reactome publishes for Reactome release 97, built into this site on 2026-09-09: the pathway list, the hierarchy relationship file and the two gene mapping files. The record card is the one live read, Reactome's own record of this pathway.

Reactome's download page describes the mapping files: Mapping files link the source database identifier to the lowest level pathway diagram or subset of the pathway, all levels of the pathway hierarchy or database identifier to all reactions. [R13] The gene list here is the all-levels mapping of NCBI Gene ids, filled from the all-levels mapping of Ensembl ids where the NCBI file has no row for a gene; each row names which file it came from by the shape of its source id. Each row carries the evidence codes the file writes for it, as written and unranked, and both where the file writes both; no page of Reactome's documentation the survey read defines the codes, so this page does not expand them. A gene id the identity files do not name is kept as the source's own id with no door rather than turned into a symbol.

On citing what a search finds, Reactome says: It should be remembered that while we strive to contain the most current and accurate data, Reactome should not be used in citations where other primary sources of information are available. [R12] The record card prints the literature Reactome attaches to a curated pathway for that reason. The data are public domain: All data in the Reactome database and files derived from that data are licensed under the Creative Commons Public Domain Dedication (CC0). User may copy, modify, and distribute these data, even for commercial purposes, without asking for permission. Attribution is encouraged but not required. [R10] The pathway illustrations are licensed apart, under CC BY 4.0, and none is shown here.

A gene on this list is one Reactome places in this pathway in this release, and that is all the row says: it does not say the gene is expressed in a tissue or associated with a disease, which are the other two explorers' questions, read from other sources. Reactome's papers of record are [R01] [R02].

[R01] Ragueneau E, Gong C, Sinquin P, Sevilla C, Beavers D, Grentner A, et al. (2026). The Reactome Knowledgebase 2026. Nucleic Acids Research 54:D673-D681. PMID 41251150, doi 10.1093/nar/gkaf1223.
[R02] Milacic M, Beavers D, Conley P, Gong C, Gillespie M, Griss J, et al. (2024). The Reactome Pathway Knowledgebase 2024. Nucleic Acids Research 52:D672-D678. PMID 37941124, doi 10.1093/nar/gkad1025.
[R10] Reactome, reactome.org. License Agreement. https://reactome.org/license, read 2026-09-09.
[R12] Reactome, reactome.org. Citing us. https://reactome.org/cite, read 2026-09-09.
[R13] Reactome, reactome.org. Download. https://reactome.org/download-data, read 2026-09-09.

Stable id: R-HSA-196807.8
Class: Pathway
Species: Homo sapiens (human)
Inferred: no: a curated human pathway
Disease pathway: no
Released: 2007-08-21
Last updated: 2021-09-15
Events inside: 28, counted from the record

Nicotinate (niacin) and nicotinamide are precursors of the coenzymes nicotinamide-adenine dinucleotide (NAD+) and nicotinamide-adenine dinucleotide phosphate (NADP+), essential cofactors in many redox reactions. The cytosolic reactions that generate NAD+ can be classified into three groups (Cambronne & Krause 2020; Covarrubias et al. 2021; Magni et al. 2004). First, in the de novo or kynurenine pathway, ACS derived from tryptophan catabolism is spontaneously converted to QUIN, which in turn is converted successively to NAMN, NAAD, and NAD+ in reactions catalyzed by QPRT, NMNAT2, and NADSYN1. These are the first four reactions listed here. Second, in the Preiss–Handler pathway, the next three reactions listed here, extracellular nicotinate (NCA), transported into the cytosol by SLC22A13 or SLC5A3, is converted to nicotinate D-ribonucleotide (NAMN), which can enter the de novo pathway to be converted to NAD+.

The remaining large group of reactions enables the modulation of nicotinamide (NAM) levels and the regeneration of NAD+ from diverse metabolic intermediates. Enzymes that play central roles in these processes include nicotinamide phosphoribosyltransferase (NAMPT), and nicotinate phosphoribosyltransferase (NAPRT1). These enzymes are poorly characterized in humans, despite their importance in NAM utilization (Magni et al. 2004). NAM levels are also regulated by nicotinamide N-methyltransferase (NNMT), a potential regulator of diet-induced obesity (Kraus et al. 2014).

Reactions mediating parts of these processes but localized to the nucleus, mitochondria, and peroxisomes are also included in this pathway.

Literature Reactome attaches

Location, Location, Location: Compartmentalization of NAD<sup>+</sup> Synthesis and Functions in Mammalian CellsTrends Biochem Sci, 2020, vol. 45, p. 858-873PubMed 32595066
NAD<sup>+</sup> metabolism and its roles in cellular processes during ageingNat Rev Mol Cell Biol, 2021, vol. 22, p. 119-141PubMed 33353981
Enzymology of NAD+ homeostasis in manCell Mol Life Sci, 2004, vol. 61, p. 19-34PubMed 14704851

Reactome's record lists 14 orthologous events, R-MMU-196807 (Mus musculus), R-RNO-196807 (Rattus norvegicus) among the species this site serves, and 12 in species this site opens no page for.

Reactome ContentService, this pathway's record · Reactome v97 · read 2026-10-01 ET · Reactome pathway browser"Nicotinate metabolism". Reactome, release 97, https://reactome.org/PathwayBrowser/#/R-HSA-196807 with StableID: R-HSA-196807.8 (accessed 2026-10-01 ET). Reactome version 97 (CC0).

Reading this pathway's record from Reactome (the pathway record).Still reading. A first read of a pathway can take a while; this page waits up to 35 seconds for it, and its scripts then bring in the panel, or a line saying what did not arrive.

02The genes

Genes Reactome places in this human pathway

The mapping files place 29 genes in this human pathway; showing 1 to 29, in pages of 100, sorted by symbol for reading. The order carries no ranking.

Genes Reactome places in this human pathway, page 1 of 1
Gene	Authority id	Mapping file id	Evidence codes
GeneBST1	AuthorityHGNC:1118	Mapping file id683 NCBI file	EvidenceTAS
GeneCD38	AuthorityHGNC:1667	Mapping file id952 NCBI file	EvidenceTAS
GeneNADK	AuthorityHGNC:29831	Mapping file id65220 NCBI file	EvidenceTAS
GeneNADK2	AuthorityHGNC:26404	Mapping file id133686 NCBI file	EvidenceTAS
GeneNADSYN1	AuthorityHGNC:29832	Mapping file id55191 NCBI file	EvidenceTAS
GeneNAMPT	AuthorityHGNC:30092	Mapping file id10135 NCBI file	EvidenceTAS
GeneNAPRT	AuthorityHGNC:30450	Mapping file id93100 NCBI file	EvidenceTAS
GeneNAXD	AuthorityHGNC:25576	Mapping file id55739 NCBI file	EvidenceTAS
GeneNAXE	AuthorityHGNC:18453	Mapping file id128240 NCBI file	EvidenceTAS
GeneNMNAT1	AuthorityHGNC:17877	Mapping file id64802 NCBI file	EvidenceTAS
GeneNMNAT2	AuthorityHGNC:16789	Mapping file id23057 NCBI file	EvidenceTAS
GeneNMNAT3	AuthorityHGNC:20989	Mapping file id349565 NCBI file	EvidenceTAS
GeneNMRK1	AuthorityHGNC:26057	Mapping file id54981 NCBI file	EvidenceTAS
GeneNMRK2	AuthorityHGNC:17871	Mapping file id27231 NCBI file	EvidenceTAS
GeneNNMT	AuthorityHGNC:7861	Mapping file id4837 NCBI file	EvidenceTAS
GeneNT5E	AuthorityHGNC:8021	Mapping file id4907 NCBI file	EvidenceTAS
GeneNUDT12	AuthorityHGNC:18826	Mapping file id83594 NCBI file	EvidenceTAS
GenePARP10	AuthorityHGNC:25895	Mapping file id84875 NCBI file	EvidenceTAS
GenePARP14	AuthorityHGNC:29232	Mapping file id54625 NCBI file	EvidenceTAS
GenePARP16	AuthorityHGNC:26040	Mapping file id54956 NCBI file	EvidenceTAS
GenePARP4	AuthorityHGNC:271	Mapping file id143 NCBI file	EvidenceTAS
GenePARP6	AuthorityHGNC:26921	Mapping file id56965 NCBI file	EvidenceTAS
GenePARP8	AuthorityHGNC:26124	Mapping file id79668 NCBI file	EvidenceTAS
GenePARP9	AuthorityHGNC:24118	Mapping file id83666 NCBI file	EvidenceTAS
GeneQPRT	AuthorityHGNC:9755	Mapping file id23475 NCBI file	EvidenceTAS
GeneRNLS	AuthorityHGNC:25641	Mapping file id55328 NCBI file	EvidenceTAS
GeneSLC22A13	AuthorityHGNC:8494	Mapping file id9390 NCBI file	EvidenceTAS
GeneSLC25A51	AuthorityHGNC:23323	Mapping file id92014 NCBI file	EvidenceTAS
GeneSLC5A8	AuthorityHGNC:19119	Mapping file id160728 NCBI file	EvidenceTAS

Evidence codes on this page: TAS, as the mapping file writes them; a row carrying two was written twice by the file, once under each. The mapping file id says which file placed the gene: an NCBI Gene id from NCBI2Reactome_All_Levels.txt, an Ensembl gene id from Ensembl2Reactome_All_Levels.txt. The two files can disagree about a code, so a row's codes are the one file's view. Measured by this site's build over this release on 2026-09-09: of the 138,908 human pathway-gene pairs both files place, 207 (0.149 per cent, over 47 genes) carry TAS in the Ensembl file where the NCBI rows carry IEA alone.

Reactome mapping files, the human rows for this pathway · Reactome release 97 · read 2026-09-09 · Reactome downloads"NCBI2Reactome_All_Levels.txt" and "Ensembl2Reactome_All_Levels.txt", Reactome, release 97, https://reactome.org/download-data/ (date of access 2026-09-09). Data CC0; attribution encouraged.

03The hierarchy

Parents and children in this release's hierarchy

Parents

Metabolism of water-soluble vitamins and cofactorsR-HSA-196849125 genes

Children

None: no pathway of this release's list names this one as a parent.

Reactome's hierarchy is a graph rather than a tree: a pathway can sit under more than one parent, and the gene counts are each pathway's own placements at every level under it, so a parent's count is not the sum of its children's.

Reactome, the human pathway list and hierarchy relationship file · Reactome release 97 · read 2026-09-09 · Reactome downloads"ReactomePathways.txt" and "ReactomePathwaysRelation.txt", Reactome, release 97, https://reactome.org/download-data/ (date of access 2026-09-09). Data CC0; attribution encouraged.