inosine-5'-phosphate biosynthesis II

MetaCyc:PWY-6124

Inosine-5'-phosphate biosynthesis II carboxylates 5-amino-1-(5-phospho-beta-D-ribosyl)imidazole directly to CAIR, ligates the carboxylate to L-aspartate, releases fumarate to form AICAR, formylates AICAR with 10-formyltetrahydrofolate, and cyclizes FAICAR to IMP.

Pathway type

nucleotide biosynthesis

Organism scope

Treponema denticola NCBITaxon:158

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Pathway network

27 nodes · 31 asserted directed edges

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Reaction / activity
Chemical / cofactor
Protein / complex
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Dashed arrow: membership, location or cofactor relation

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Components and activities

Declared biological components and source reaction directions
Node	Kind or role	Source direction
Treponema denticola `NCBITaxon:158`	taxon
phosphoribosylaminoimidazole carboxylase `EC:4.1.1.21`	molecular activity
phosphoribosylaminoimidazolesuccinocarboxamide synthase `EC:6.3.2.6`	molecular activity
adenylosuccinate lyase `EC:4.3.2.2`	molecular activity
phosphoribosylaminoimidazolecarboxamide formyltransferase `EC:2.1.2.3`	molecular activity
IMP cyclohydrolase `EC:3.5.4.10`	molecular activity
5-amino-1-(5-phospho-beta-D-ribosyl)imidazole `CHEBI:137981`	small molecule
CO2 `CHEBI:16526`	small molecule
5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate `CHEBI:77657`	small molecule
H(+) `CHEBI:15378`	small molecule
L-aspartate `CHEBI:29991`	small molecule
ATP `CHEBI:30616`	small molecule
(2S)-2-[5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamido]succinate `CHEBI:58443`	small molecule
ADP `CHEBI:456216`	small molecule
phosphate `CHEBI:43474`	small molecule
5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamide `CHEBI:58475`	small molecule
fumarate `CHEBI:29806`	small molecule
(6R)-10-formyltetrahydrofolate `CHEBI:195366`	small molecule
5-formamido-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide `CHEBI:58467`	small molecule
(6S)-5,6,7,8-tetrahydrofolate `CHEBI:57453`	small molecule
IMP `CHEBI:58053`	small molecule
H2O `CHEBI:15377`	small molecule
Phosphoribosylaminoimidazole carboxylase `UniProtKB:Q73PV9`	protein
phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	reaction	left to right
adenylosuccinate lyase SAICAR-cleavage reaction `RHEA:23921`	reaction	left to right
AICAR transformylase reaction `RHEA:22193`	reaction	left to right
IMP cyclohydrolase reaction `RHEA:18447`	reaction	right to left
phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	reaction	right to left

Mechanistic edges

Mechanistic edges and their cited evidence
Subject	Predicate and description	Object	Evidence
L-aspartate `CHEBI:29991`	consumes	phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	RHEA:22629 Source assertion: Rhea lists CHEBI:29991 on the substrates side of RHEA:22629 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22629']/rh:substrates; rh:contains/rh:compound/rh:accession`
ATP `CHEBI:30616`	consumes	phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	RHEA:22629 Source assertion: Rhea lists CHEBI:30616 on the substrates side of RHEA:22629 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22629']/rh:substrates; rh:contains/rh:compound/rh:accession`
5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate `CHEBI:77657`	consumes	phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	RHEA:22629 Source assertion: Rhea lists CHEBI:77657 on the substrates side of RHEA:22629 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22629']/rh:substrates; rh:contains/rh:compound/rh:accession`
phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	produces	H(+) `CHEBI:15378`	RHEA:22629 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:22629 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22629']/rh:products; rh:contains/rh:compound/rh:accession`
phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	produces	phosphate `CHEBI:43474`	RHEA:22629 Source assertion: Rhea lists CHEBI:43474 on the products side of RHEA:22629 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22629']/rh:products; rh:contains/rh:compound/rh:accession`
phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	produces	ADP `CHEBI:456216`	RHEA:22629 Source assertion: Rhea lists CHEBI:456216 on the products side of RHEA:22629 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22629']/rh:products; rh:contains/rh:compound/rh:accession`
phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	produces	(2S)-2-[5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamido]succinate `CHEBI:58443`	RHEA:22629 Source assertion: Rhea lists CHEBI:58443 on the products side of RHEA:22629 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22629']/rh:products; rh:contains/rh:compound/rh:accession`
(2S)-2-[5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamido]succinate `CHEBI:58443`	consumes	adenylosuccinate lyase SAICAR-cleavage reaction `RHEA:23921`	RHEA:23921 Source assertion: Rhea lists CHEBI:58443 on the substrates side of RHEA:23921 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23921']/rh:substrates; rh:contains/rh:compound/rh:accession`
adenylosuccinate lyase SAICAR-cleavage reaction `RHEA:23921`	produces	fumarate `CHEBI:29806`	RHEA:23921 Source assertion: Rhea lists CHEBI:29806 on the products side of RHEA:23921 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23921']/rh:products; rh:contains/rh:compound/rh:accession`
adenylosuccinate lyase SAICAR-cleavage reaction `RHEA:23921`	produces	5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamide `CHEBI:58475`	RHEA:23921 Source assertion: Rhea lists CHEBI:58475 on the products side of RHEA:23921 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/23921']/rh:products; rh:contains/rh:compound/rh:accession`
(6R)-10-formyltetrahydrofolate `CHEBI:195366`	consumes	AICAR transformylase reaction `RHEA:22193`	RHEA:22193 Source assertion: Rhea lists CHEBI:195366 on the substrates side of RHEA:22193 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22193']/rh:substrates; rh:contains/rh:compound/rh:accession`
5-amino-1-(5-phospho-beta-D-ribosyl)imidazole-4-carboxamide `CHEBI:58475`	consumes	AICAR transformylase reaction `RHEA:22193`	RHEA:22193 Source assertion: Rhea lists CHEBI:58475 on the substrates side of RHEA:22193 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22193']/rh:substrates; rh:contains/rh:compound/rh:accession`
AICAR transformylase reaction `RHEA:22193`	produces	(6S)-5,6,7,8-tetrahydrofolate `CHEBI:57453`	RHEA:22193 Source assertion: Rhea lists CHEBI:57453 on the products side of RHEA:22193 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22193']/rh:products; rh:contains/rh:compound/rh:accession`
AICAR transformylase reaction `RHEA:22193`	produces	5-formamido-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide `CHEBI:58467`	RHEA:22193 Source assertion: Rhea lists CHEBI:58467 on the products side of RHEA:22193 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/22193']/rh:products; rh:contains/rh:compound/rh:accession`
5-formamido-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide `CHEBI:58467`	consumes	IMP cyclohydrolase reaction `RHEA:18447`	RHEA:18447 Source assertion: Rhea lists CHEBI:58467 on the substrates side of RHEA:18447 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/18447']/rh:substrates; rh:contains/rh:compound/rh:accession`
IMP cyclohydrolase reaction `RHEA:18447`	produces	H2O `CHEBI:15377`	RHEA:18447 Source assertion: Rhea lists CHEBI:15377 on the products side of RHEA:18447 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/18447']/rh:products; rh:contains/rh:compound/rh:accession`
IMP cyclohydrolase reaction `RHEA:18447`	produces	IMP `CHEBI:58053`	RHEA:18447 Source assertion: Rhea lists CHEBI:58053 on the products side of RHEA:18447 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/18447']/rh:products; rh:contains/rh:compound/rh:accession`
5-amino-1-(5-phospho-beta-D-ribosyl)imidazole `CHEBI:137981`	consumes	phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	RHEA:10794 Source assertion: Rhea lists CHEBI:137981 on the substrates side of RHEA:10794 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10794']/rh:substrates; rh:contains/rh:compound/rh:accession`
CO2 `CHEBI:16526`	consumes	phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	RHEA:10794 Source assertion: Rhea lists CHEBI:16526 on the substrates side of RHEA:10794 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10794']/rh:substrates; rh:contains/rh:compound/rh:accession`
phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	produces	H(+) `CHEBI:15378`	RHEA:10794 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:10794 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10794']/rh:products; rh:contains/rh:compound/rh:accession`
phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	produces	5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate `CHEBI:77657`	RHEA:10794 Source assertion: Rhea lists CHEBI:77657 on the products side of RHEA:10794 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10794']/rh:products; rh:contains/rh:compound/rh:accession`
phosphoribosylaminoimidazole carboxylase `EC:4.1.1.21`	catalyzes	phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	RHEA:10792 Source assertion: Rhea associates EC:4.1.1.21 with the reaction family containing RHEA:10794. Source location `rh:ec` PMID:21548610 Source assertion: The study demonstrates AIR carboxylase activity of class II PurE in Treponema denticola, supporting the direct AIR-to-CAIR route in this bacterial taxon. Source location `PubMed Abstract; purified TdPurE catalytic activity`
phosphoribosylaminoimidazolesuccinocarboxamide synthase `EC:6.3.2.6`	catalyzes	phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	RHEA:22628 Source assertion: Rhea associates EC:6.3.2.6 with the reaction family containing RHEA:22629. Source location `rh:ec`
adenylosuccinate lyase `EC:4.3.2.2`	catalyzes	adenylosuccinate lyase SAICAR-cleavage reaction `RHEA:23921`	RHEA:23920 Source assertion: Rhea associates EC:4.3.2.2 with the reaction family containing RHEA:23921. Source location `rh:ec`
phosphoribosylaminoimidazolecarboxamide formyltransferase `EC:2.1.2.3`	catalyzes	AICAR transformylase reaction `RHEA:22193`	RHEA:22192 Source assertion: Rhea associates EC:2.1.2.3 with the reaction family containing RHEA:22193. Source location `rh:ec`
IMP cyclohydrolase `EC:3.5.4.10`	catalyzes	IMP cyclohydrolase reaction `RHEA:18447`	RHEA:18445 Source assertion: Rhea associates EC:3.5.4.10 with the reaction family containing RHEA:18447. Source location `rh:ec`
phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	precedes	phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	MetaCyc:PWY-6124 Source assertion: MetaCyc pathway ordering places RHEA:10794 before RHEA:22629 in this pathway. Shared intermediate: CHEBI:77657. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
AICAR transformylase reaction `RHEA:22193`	precedes	IMP cyclohydrolase reaction `RHEA:18447`	MetaCyc:PWY-6124 Source assertion: MetaCyc pathway ordering places RHEA:22193 before RHEA:18447 in this pathway. Shared intermediate: CHEBI:58467. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
phosphoribosylaminoimidazolesuccinocarboxamide synthase reaction `RHEA:22629`	precedes	adenylosuccinate lyase SAICAR-cleavage reaction `RHEA:23921`	MetaCyc:PWY-6124 Source assertion: MetaCyc pathway ordering places RHEA:22629 before RHEA:23921 in this pathway. Shared intermediate: CHEBI:58443. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
adenylosuccinate lyase SAICAR-cleavage reaction `RHEA:23921`	precedes	AICAR transformylase reaction `RHEA:22193`	MetaCyc:PWY-6124 Source assertion: MetaCyc pathway ordering places RHEA:23921 before RHEA:22193 in this pathway. Shared intermediate: CHEBI:58475. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
Phosphoribosylaminoimidazole carboxylase `UniProtKB:Q73PV9`	enables	phosphoribosylaminoimidazole carboxylase reaction `RHEA:10794`	UniProtKB:Q73PV9 Source assertion: UniProt annotates UniProtKB:Q73PV9 with catalytic activity for the reaction family of RHEA:10794. Annotation evidence: ECO:0000255, ECO:0000269; organism taxon: NCBITaxon:243275. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`

References

MetaCyc:PWY-6124 MetaCyc inosine-5'-phosphate biosynthesis II pathway (source version: 22.5)
RHEA:10792 Rhea phosphoribosylaminoimidazole carboxylase reaction (source version: 139)
RHEA:10795 Rhea CAIR/AIR carboxylase bidirectional reaction (source version: 139)
RHEA:22628 Rhea SAICAR synthetase reaction (source version: 139)
RHEA:22629 Rhea SAICAR-forming direction (source version: 139)
RHEA:23920 Rhea adenylosuccinate lyase AICAR-forming reaction (source version: 139)
RHEA:23921 Rhea AICAR-forming direction (source version: 139)
RHEA:22192 Rhea AICAR transformylase reaction (source version: 139)
RHEA:22193 Rhea FAICAR-forming direction (source version: 139)
RHEA:18445 Rhea IMP cyclohydrolase reaction (source version: 139)
RHEA:18447 Rhea IMP-forming direction (source version: 139)
RHEA:10794 RHEA:10794 authority record (source version: 139)
UniProtKB:Q73PV9 UniProtKB:Q73PV9 authority record (source version: 2026_03)
PMID:21548610 PMID:21548610 authority record

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 5 to 5; 1 directed-ID corrections; 1 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.
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