NAD salvage pathway I (PNC VI cycle)

MetaCyc:PYRIDNUCSAL-PWY

NAD salvage pathway I cycles NAD(+) through beta-nicotinamide D-ribonucleotide, nicotinamide, nicotinate, nicotinate beta-D-ribonucleotide, and deamido-NAD(+) before glutamine-dependent amidation regenerates NAD(+).

Pathway type

cofactor biosynthesis

Organism scope

Bacteria NCBITaxon:2

Read the source YAML

Pathway network

30 nodes · 48 asserted directed edges

Arrows show recorded subject → object relationships, not necessarily metabolic flow. Select a node for details or an arrow for evidence. Scroll, zoom or find a node to explore.

Reaction / activity
Chemical / cofactor
Other participant
Solid arrow: mechanistic relation
Dashed arrow: membership, location or cofactor relation

Show at full size (scroll to explore)

Components and activities

Declared biological components and source reaction directions
Node	Kind or role	Source direction
Bacteria `NCBITaxon:2`	taxon
NAD(+) diphosphatase `EC:3.6.1.22`	molecular activity
NMN nucleosidase `EC:3.2.2.14`	molecular activity
nicotinamidase `EC:3.5.1.19`	molecular activity
nicotinate phosphoribosyltransferase `EC:6.3.4.21`	molecular activity
nicotinate-nucleotide adenylyltransferase `EC:2.7.7.18`	molecular activity
NAD(+) synthase (glutamine-hydrolyzing) `EC:6.3.5.1`	molecular activity
NAD(+) `CHEBI:57540`	small molecule
H2O `CHEBI:15377`	small molecule
beta-nicotinamide D-ribonucleotide `CHEBI:14649`	small molecule
AMP `CHEBI:456215`	small molecule
H(+) `CHEBI:15378`	small molecule
D-ribose 5-phosphate `CHEBI:78346`	small molecule
nicotinamide `CHEBI:17154`	small molecule
nicotinate `CHEBI:32544`	small molecule
NH4(+) `CHEBI:28938`	small molecule
5-phospho-alpha-D-ribose 1-diphosphate `CHEBI:58017`	small molecule
ATP `CHEBI:30616`	small molecule
nicotinate beta-D-ribonucleotide `CHEBI:57502`	small molecule
ADP `CHEBI:456216`	small molecule
phosphate `CHEBI:43474`	small molecule
diphosphate `CHEBI:33019`	small molecule
deamido-NAD(+) `CHEBI:58437`	small molecule
L-glutamine `CHEBI:58359`	small molecule
L-glutamate `CHEBI:29985`	small molecule
NAD(+) diphosphatase reaction `RHEA:11801`	reaction	left to right
NMN nucleosidase reaction `RHEA:23141`	reaction	left to right
nicotinamidase reaction `RHEA:14546`	reaction	left to right
nicotinate phosphoribosyltransferase reaction `RHEA:36164`	reaction	left to right
nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	reaction	left to right
glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	reaction	left to right

Mechanistic edges

Mechanistic edges and their cited evidence
Subject	Predicate and description	Object	Evidence
H2O `CHEBI:15377`	consumes	NAD(+) diphosphatase reaction `RHEA:11801`	RHEA:11801 Source assertion: Rhea lists CHEBI:15377 on the substrates side of RHEA:11801 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11801']/rh:substrates; rh:contains/rh:compound/rh:accession`
NAD(+) `CHEBI:57540`	consumes	NAD(+) diphosphatase reaction `RHEA:11801`	RHEA:11801 Source assertion: Rhea lists CHEBI:57540 on the substrates side of RHEA:11801 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11801']/rh:substrates; rh:contains/rh:compound/rh:accession`
NAD(+) diphosphatase reaction `RHEA:11801`	produces	beta-nicotinamide D-ribonucleotide `CHEBI:14649`	RHEA:11801 Source assertion: Rhea lists CHEBI:14649 on the products side of RHEA:11801 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11801']/rh:products; rh:contains/rh:compound/rh:accession`
NAD(+) diphosphatase reaction `RHEA:11801`	produces	H(+) `CHEBI:15378`	RHEA:11801 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:11801 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11801']/rh:products; rh:contains/rh:compound/rh:accession`
NAD(+) diphosphatase reaction `RHEA:11801`	produces	AMP `CHEBI:456215`	RHEA:11801 Source assertion: Rhea lists CHEBI:456215 on the products side of RHEA:11801 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/11801']/rh:products; rh:contains/rh:compound/rh:accession`
beta-nicotinamide D-ribonucleotide `CHEBI:14649`	consumes	NMN nucleosidase reaction `RHEA:23141`	RHEA:23141 Source assertion: Rhea lists CHEBI:14649 on the substrates side of RHEA:23141 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23141']/rh:substrates; rh:contains/rh:compound/rh:accession`
H2O `CHEBI:15377`	consumes	NMN nucleosidase reaction `RHEA:23141`	RHEA:23141 Source assertion: Rhea lists CHEBI:15377 on the substrates side of RHEA:23141 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23141']/rh:substrates; rh:contains/rh:compound/rh:accession`
NMN nucleosidase reaction `RHEA:23141`	produces	H(+) `CHEBI:15378`	RHEA:23141 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:23141 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23141']/rh:products; rh:contains/rh:compound/rh:accession`
NMN nucleosidase reaction `RHEA:23141`	produces	nicotinamide `CHEBI:17154`	RHEA:23141 Source assertion: Rhea lists CHEBI:17154 on the products side of RHEA:23141 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23141']/rh:products; rh:contains/rh:compound/rh:accession`
NMN nucleosidase reaction `RHEA:23141`	produces	D-ribose 5-phosphate `CHEBI:78346`	RHEA:23141 Source assertion: Rhea lists CHEBI:78346 on the products side of RHEA:23141 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23141']/rh:products; rh:contains/rh:compound/rh:accession`
H2O `CHEBI:15377`	consumes	nicotinamidase reaction `RHEA:14546`	RHEA:14546 Source assertion: Rhea lists CHEBI:15377 on the substrates side of RHEA:14546 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/14546']/rh:substrates; rh:contains/rh:compound/rh:accession`
nicotinamide `CHEBI:17154`	consumes	nicotinamidase reaction `RHEA:14546`	RHEA:14546 Source assertion: Rhea lists CHEBI:17154 on the substrates side of RHEA:14546 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/14546']/rh:substrates; rh:contains/rh:compound/rh:accession`
nicotinamidase reaction `RHEA:14546`	produces	NH4(+) `CHEBI:28938`	RHEA:14546 Source assertion: Rhea lists CHEBI:28938 on the products side of RHEA:14546 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/14546']/rh:products; rh:contains/rh:compound/rh:accession`
nicotinamidase reaction `RHEA:14546`	produces	nicotinate `CHEBI:32544`	RHEA:14546 Source assertion: Rhea lists CHEBI:32544 on the products side of RHEA:14546 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/14546']/rh:products; rh:contains/rh:compound/rh:accession`
H2O `CHEBI:15377`	consumes	nicotinate phosphoribosyltransferase reaction `RHEA:36164`	RHEA:36164 Source assertion: Rhea lists CHEBI:15377 on the substrates side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:substrates; rh:contains/rh:compound/rh:accession`
ATP `CHEBI:30616`	consumes	nicotinate phosphoribosyltransferase reaction `RHEA:36164`	RHEA:36164 Source assertion: Rhea lists CHEBI:30616 on the substrates side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:substrates; rh:contains/rh:compound/rh:accession`
nicotinate `CHEBI:32544`	consumes	nicotinate phosphoribosyltransferase reaction `RHEA:36164`	RHEA:36164 Source assertion: Rhea lists CHEBI:32544 on the substrates side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:substrates; rh:contains/rh:compound/rh:accession`
5-phospho-alpha-D-ribose 1-diphosphate `CHEBI:58017`	consumes	nicotinate phosphoribosyltransferase reaction `RHEA:36164`	RHEA:36164 Source assertion: Rhea lists CHEBI:58017 on the substrates side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:substrates; rh:contains/rh:compound/rh:accession`
nicotinate phosphoribosyltransferase reaction `RHEA:36164`	produces	diphosphate `CHEBI:33019`	RHEA:36164 Source assertion: Rhea lists CHEBI:33019 on the products side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:products; rh:contains/rh:compound/rh:accession`
nicotinate phosphoribosyltransferase reaction `RHEA:36164`	produces	phosphate `CHEBI:43474`	RHEA:36164 Source assertion: Rhea lists CHEBI:43474 on the products side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:products; rh:contains/rh:compound/rh:accession`
nicotinate phosphoribosyltransferase reaction `RHEA:36164`	produces	ADP `CHEBI:456216`	RHEA:36164 Source assertion: Rhea lists CHEBI:456216 on the products side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:products; rh:contains/rh:compound/rh:accession`
nicotinate phosphoribosyltransferase reaction `RHEA:36164`	produces	nicotinate beta-D-ribonucleotide `CHEBI:57502`	RHEA:36164 Source assertion: Rhea lists CHEBI:57502 on the products side of RHEA:36164 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/36164']/rh:products; rh:contains/rh:compound/rh:accession`
H(+) `CHEBI:15378`	consumes	nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	RHEA:22861 Source assertion: Rhea lists CHEBI:15378 on the substrates side of RHEA:22861 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22861']/rh:substrates; rh:contains/rh:compound/rh:accession`
ATP `CHEBI:30616`	consumes	nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	RHEA:22861 Source assertion: Rhea lists CHEBI:30616 on the substrates side of RHEA:22861 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22861']/rh:substrates; rh:contains/rh:compound/rh:accession`
nicotinate beta-D-ribonucleotide `CHEBI:57502`	consumes	nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	RHEA:22861 Source assertion: Rhea lists CHEBI:57502 on the substrates side of RHEA:22861 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22861']/rh:substrates; rh:contains/rh:compound/rh:accession`
nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	produces	diphosphate `CHEBI:33019`	RHEA:22861 Source assertion: Rhea lists CHEBI:33019 on the products side of RHEA:22861 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22861']/rh:products; rh:contains/rh:compound/rh:accession`
nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	produces	deamido-NAD(+) `CHEBI:58437`	RHEA:22861 Source assertion: Rhea lists CHEBI:58437 on the products side of RHEA:22861 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22861']/rh:products; rh:contains/rh:compound/rh:accession`
H2O `CHEBI:15377`	consumes	glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	RHEA:24385 Source assertion: Rhea lists CHEBI:15377 on the substrates side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:substrates; rh:contains/rh:compound/rh:accession`
ATP `CHEBI:30616`	consumes	glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	RHEA:24385 Source assertion: Rhea lists CHEBI:30616 on the substrates side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:substrates; rh:contains/rh:compound/rh:accession`
L-glutamine `CHEBI:58359`	consumes	glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	RHEA:24385 Source assertion: Rhea lists CHEBI:58359 on the substrates side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:substrates; rh:contains/rh:compound/rh:accession`
deamido-NAD(+) `CHEBI:58437`	consumes	glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	RHEA:24385 Source assertion: Rhea lists CHEBI:58437 on the substrates side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:substrates; rh:contains/rh:compound/rh:accession`
glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	produces	H(+) `CHEBI:15378`	RHEA:24385 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:products; rh:contains/rh:compound/rh:accession`
glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	produces	L-glutamate `CHEBI:29985`	RHEA:24385 Source assertion: Rhea lists CHEBI:29985 on the products side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:products; rh:contains/rh:compound/rh:accession`
glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	produces	diphosphate `CHEBI:33019`	RHEA:24385 Source assertion: Rhea lists CHEBI:33019 on the products side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:products; rh:contains/rh:compound/rh:accession`
glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	produces	AMP `CHEBI:456215`	RHEA:24385 Source assertion: Rhea lists CHEBI:456215 on the products side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:products; rh:contains/rh:compound/rh:accession`
glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	produces	NAD(+) `CHEBI:57540`	RHEA:24385 Source assertion: Rhea lists CHEBI:57540 on the products side of RHEA:24385 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/24385']/rh:products; rh:contains/rh:compound/rh:accession`
NAD(+) diphosphatase `EC:3.6.1.22`	catalyzes	NAD(+) diphosphatase reaction `RHEA:11801`	RHEA:11800 Source assertion: Rhea associates EC:3.6.1.22 with the reaction family containing RHEA:11801. Source location `rh:ec`
NMN nucleosidase `EC:3.2.2.14`	catalyzes	NMN nucleosidase reaction `RHEA:23141`	RHEA:23140 Source assertion: Rhea associates EC:3.2.2.14 with the reaction family containing RHEA:23141. Source location `rh:ec`
nicotinamidase `EC:3.5.1.19`	catalyzes	nicotinamidase reaction `RHEA:14546`	RHEA:14545 Source assertion: Rhea associates EC:3.5.1.19 with the reaction family containing RHEA:14546. Source location `rh:ec`
nicotinate phosphoribosyltransferase `EC:6.3.4.21`	catalyzes	nicotinate phosphoribosyltransferase reaction `RHEA:36164`	RHEA:36163 Source assertion: Rhea associates EC:6.3.4.21 with the reaction family containing RHEA:36164. Source location `rh:ec`
nicotinate-nucleotide adenylyltransferase `EC:2.7.7.18`	catalyzes	nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	RHEA:22860 Source assertion: Rhea associates EC:2.7.7.18 with the reaction family containing RHEA:22861. Source location `rh:ec`
NAD(+) synthase (glutamine-hydrolyzing) `EC:6.3.5.1`	catalyzes	glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	RHEA:24384 Source assertion: Rhea associates EC:6.3.5.1 with the reaction family containing RHEA:24385. Source location `rh:ec`
NAD(+) diphosphatase reaction `RHEA:11801`	precedes	NMN nucleosidase reaction `RHEA:23141`	MetaCyc:PYRIDNUCSAL-PWY Source assertion: MetaCyc pathway ordering places RHEA:11801 before RHEA:23141 in this pathway. Shared intermediate: CHEBI:14649. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
nicotinamidase reaction `RHEA:14546`	precedes	nicotinate phosphoribosyltransferase reaction `RHEA:36164`	MetaCyc:PYRIDNUCSAL-PWY Source assertion: MetaCyc pathway ordering places RHEA:14546 before RHEA:36164 in this pathway. Shared intermediate: CHEBI:32544. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	precedes	glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	MetaCyc:PYRIDNUCSAL-PWY Source assertion: MetaCyc pathway ordering places RHEA:22861 before RHEA:24385 in this pathway. Shared intermediate: CHEBI:58437. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
NMN nucleosidase reaction `RHEA:23141`	precedes	nicotinamidase reaction `RHEA:14546`	MetaCyc:PYRIDNUCSAL-PWY Source assertion: MetaCyc pathway ordering places RHEA:23141 before RHEA:14546 in this pathway. Shared intermediate: CHEBI:17154. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
glutamine-dependent NAD(+) synthase reaction `RHEA:24385`	precedes	NAD(+) diphosphatase reaction `RHEA:11801`	MetaCyc:PYRIDNUCSAL-PWY Source assertion: MetaCyc pathway ordering places RHEA:24385 before RHEA:11801 in this pathway. The source ordering may bridge anomer-specific and broader substrate classes. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
nicotinate phosphoribosyltransferase reaction `RHEA:36164`	precedes	nicotinate-nucleotide adenylyltransferase reaction `RHEA:22861`	MetaCyc:PYRIDNUCSAL-PWY Source assertion: MetaCyc pathway ordering places RHEA:36164 before RHEA:22861 in this pathway. Shared intermediate: CHEBI:57502. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`

References

MetaCyc:PYRIDNUCSAL-PWY MetaCyc NAD salvage pathway I (source version: 22.5)
RHEA:11800 Rhea NAD(+) diphosphatase reaction (source version: 139)
RHEA:11801 Rhea beta-nicotinamide D-ribonucleotide-forming direction (source version: 139)
RHEA:23140 Rhea NMN nucleosidase reaction (source version: 139)
RHEA:23141 Rhea nicotinamide-forming direction (source version: 139)
RHEA:14545 Rhea nicotinamidase reaction (source version: 139)
RHEA:14546 Rhea nicotinate-forming direction (source version: 139)
RHEA:36163 Rhea nicotinate phosphoribosyltransferase reaction (source version: 139)
RHEA:36164 Rhea nicotinate beta-D-ribonucleotide-forming direction (source version: 139)
RHEA:22860 Rhea nicotinate-nucleotide adenylyltransferase reaction (source version: 139)
RHEA:22861 Rhea deamido-NAD-forming direction (source version: 139)
RHEA:24384 Rhea glutamine-dependent NAD synthase reaction (source version: 139)
RHEA:24385 Rhea NAD-forming glutamine-dependent direction (source version: 139)

Curation history

2026-10-05T06:25:52Z codex
- EDIT — Review causal chemistry and add sourced molecular context
  Reviewed the entire record against MetaCyc 22.5 native pathway XML (including nested pathways), Rhea 139 explicit sides and directions, ENZYME 02-Sep-2026, PubMed records, and reviewed UniProt 2026_03 annotations within the record's taxon scope. Replaced generated structured-source quotations with source_assertion and source_locator. Typed molecular activities and participants. Reaction count 6 to 6; 0 directed-ID corrections; 0 protein annotations, 0 cofactor annotations and 0 sourced locations. All Rhea reaction substrate/product sets checked against independent Rhea authority; native pathway leaf coverage and source exceptions recorded in reports/causal_graph_review/metacyc-review.json. Full source URLs, versions and byte hashes are in metacyc-sources.json. All 50 MetaCyc records passed native schema validation; six targeted chemistry/evidence regression tests passed. Missing protein or cofactor annotations are not treated as biological absence; qualifications and exclusions are preserved in the ledger.
Read this curation session