pentose phosphate pathway (oxidative branch) I

MetaCyc:OXIDATIVEPENT-PWY

The oxidative branch of the pentose phosphate pathway oxidizes D-glucose 6-phosphate to 6-phospho-D-gluconate via 6-phospho-D-glucono-1,5-lactone, then oxidatively decarboxylates 6-phospho-D-gluconate to D-ribulose 5-phosphate while reducing NADP(+) to NADPH.

Pathway type

central carbon metabolism

Organism scope

Escherichia coli NCBITaxon:562

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Pathway network

18 nodes · 22 asserted directed edges

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Reaction / activity
Chemical / cofactor
Protein / complex
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Solid arrow: mechanistic relation
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
Escherichia coli `NCBITaxon:562`	taxon
glucose-6-phosphate dehydrogenase `EC:1.1.1.49`	molecular activity
6-phosphogluconolactonase `EC:3.1.1.31`	molecular activity
6-phosphogluconate dehydrogenase `EC:1.1.1.44`	molecular activity
D-glucose 6-phosphate `CHEBI:61548`	small molecule
NADP(+) `CHEBI:58349`	small molecule
6-phospho-D-glucono-1,5-lactone `CHEBI:57955`	small molecule
NADPH `CHEBI:57783`	small molecule
H(+) `CHEBI:15378`	small molecule
H2O `CHEBI:15377`	small molecule
6-phospho-D-gluconate `CHEBI:58759`	small molecule
D-ribulose 5-phosphate `CHEBI:58121`	small molecule
CO2 `CHEBI:16526`	small molecule
6-phosphogluconate dehydrogenase, decarboxylating `UniProtKB:P00350`	protein
Glucose-6-phosphate 1-dehydrogenase `UniProtKB:P0AC53`	protein
6-phosphogluconolactonase `UniProtKB:P52697`	protein
glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	reaction	left to right
6-phosphogluconolactonase reaction `RHEA:12557`	reaction	left to right
6-phosphogluconate dehydrogenase reaction `RHEA:10117`	reaction	left to right

Mechanistic edges

Mechanistic edges and their cited evidence
Subject	Predicate and description	Object	Evidence
NADP(+) `CHEBI:58349`	consumes	glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	RHEA:15842 Source assertion: Rhea lists CHEBI:58349 on the substrates side of RHEA:15842 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/15842']/rh:substrates; rh:contains/rh:compound/rh:accession`
D-glucose 6-phosphate `CHEBI:61548`	consumes	glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	RHEA:15842 Source assertion: Rhea lists CHEBI:61548 on the substrates side of RHEA:15842 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/15842']/rh:substrates; rh:contains/rh:compound/rh:accession`
glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	produces	H(+) `CHEBI:15378`	RHEA:15842 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:15842 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/15842']/rh:products; rh:contains/rh:compound/rh:accession`
glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	produces	NADPH `CHEBI:57783`	RHEA:15842 Source assertion: Rhea lists CHEBI:57783 on the products side of RHEA:15842 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/15842']/rh:products; rh:contains/rh:compound/rh:accession`
glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	produces	6-phospho-D-glucono-1,5-lactone `CHEBI:57955`	RHEA:15842 Source assertion: Rhea lists CHEBI:57955 on the products side of RHEA:15842 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/15842']/rh:products; rh:contains/rh:compound/rh:accession`
H2O `CHEBI:15377`	consumes	6-phosphogluconolactonase reaction `RHEA:12557`	RHEA:12557 Source assertion: Rhea lists CHEBI:15377 on the substrates side of RHEA:12557 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/12557']/rh:substrates; rh:contains/rh:compound/rh:accession`
6-phospho-D-glucono-1,5-lactone `CHEBI:57955`	consumes	6-phosphogluconolactonase reaction `RHEA:12557`	RHEA:12557 Source assertion: Rhea lists CHEBI:57955 on the substrates side of RHEA:12557 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/12557']/rh:substrates; rh:contains/rh:compound/rh:accession`
6-phosphogluconolactonase reaction `RHEA:12557`	produces	H(+) `CHEBI:15378`	RHEA:12557 Source assertion: Rhea lists CHEBI:15378 on the products side of RHEA:12557 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/12557']/rh:products; rh:contains/rh:compound/rh:accession`
6-phosphogluconolactonase reaction `RHEA:12557`	produces	6-phospho-D-gluconate `CHEBI:58759`	RHEA:12557 Source assertion: Rhea lists CHEBI:58759 on the products side of RHEA:12557 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/12557']/rh:products; rh:contains/rh:compound/rh:accession`
NADP(+) `CHEBI:58349`	consumes	6-phosphogluconate dehydrogenase reaction `RHEA:10117`	RHEA:10117 Source assertion: Rhea lists CHEBI:58349 on the substrates side of RHEA:10117 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10117']/rh:substrates; rh:contains/rh:compound/rh:accession`
6-phospho-D-gluconate `CHEBI:58759`	consumes	6-phosphogluconate dehydrogenase reaction `RHEA:10117`	RHEA:10117 Source assertion: Rhea lists CHEBI:58759 on the substrates side of RHEA:10117 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10117']/rh:substrates; rh:contains/rh:compound/rh:accession`
6-phosphogluconate dehydrogenase reaction `RHEA:10117`	produces	CO2 `CHEBI:16526`	RHEA:10117 Source assertion: Rhea lists CHEBI:16526 on the products side of RHEA:10117 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10117']/rh:products; rh:contains/rh:compound/rh:accession`
6-phosphogluconate dehydrogenase reaction `RHEA:10117`	produces	NADPH `CHEBI:57783`	RHEA:10117 Source assertion: Rhea lists CHEBI:57783 on the products side of RHEA:10117 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10117']/rh:products; rh:contains/rh:compound/rh:accession`
6-phosphogluconate dehydrogenase reaction `RHEA:10117`	produces	D-ribulose 5-phosphate `CHEBI:58121`	RHEA:10117 Source assertion: Rhea lists CHEBI:58121 on the products side of RHEA:10117 in this directed reaction. Source location `rdf:Description[@rdf:about='http://rdf.rhea-db.org/10117']/rh:products; rh:contains/rh:compound/rh:accession`
glucose-6-phosphate dehydrogenase `EC:1.1.1.49`	catalyzes	glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	RHEA:15841 Source assertion: Rhea associates EC:1.1.1.49 with the reaction family containing RHEA:15842. Source location `rh:ec`
6-phosphogluconolactonase `EC:3.1.1.31`	catalyzes	6-phosphogluconolactonase reaction `RHEA:12557`	RHEA:12556 Source assertion: Rhea associates EC:3.1.1.31 with the reaction family containing RHEA:12557. Source location `rh:ec`
6-phosphogluconate dehydrogenase `EC:1.1.1.44`	catalyzes	6-phosphogluconate dehydrogenase reaction `RHEA:10117`	RHEA:10116 Source assertion: Rhea associates EC:1.1.1.44 with the reaction family containing RHEA:10117. Source location `rh:ec`
6-phosphogluconolactonase reaction `RHEA:12557`	precedes	6-phosphogluconate dehydrogenase reaction `RHEA:10117`	MetaCyc:OXIDATIVEPENT-PWY Source assertion: MetaCyc pathway ordering places RHEA:12557 before RHEA:10117 in this pathway. Shared intermediate: CHEBI:58759. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	precedes	6-phosphogluconolactonase reaction `RHEA:12557`	MetaCyc:OXIDATIVEPENT-PWY Source assertion: MetaCyc pathway ordering places RHEA:15842 before RHEA:12557 in this pathway. Shared intermediate: CHEBI:57955. Source location `Pathway/reaction-ordering and reaction-layout; Rhea-to-MetaCyc cross-references`
6-phosphogluconate dehydrogenase, decarboxylating `UniProtKB:P00350`	enables	6-phosphogluconate dehydrogenase reaction `RHEA:10117`	UniProtKB:P00350 Source assertion: UniProt annotates UniProtKB:P00350 with catalytic activity for the reaction family of RHEA:10117. Annotation evidence: ECO:0000269; organism taxon: NCBITaxon:83333. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`
Glucose-6-phosphate 1-dehydrogenase `UniProtKB:P0AC53`	enables	glucose-6-phosphate dehydrogenase reaction `RHEA:15842`	UniProtKB:P0AC53 Source assertion: UniProt annotates UniProtKB:P0AC53 with catalytic activity for the reaction family of RHEA:15842. Annotation evidence: ECO:0000255; organism taxon: NCBITaxon:83333. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`
6-phosphogluconolactonase `UniProtKB:P52697`	enables	6-phosphogluconolactonase reaction `RHEA:12557`	UniProtKB:P52697 Source assertion: UniProt annotates UniProtKB:P52697 with catalytic activity for the reaction family of RHEA:12557. Annotation evidence: ECO:0000269; organism taxon: NCBITaxon:83333. Source location `comments[commentType='CATALYTIC ACTIVITY'].reaction.reactionCrossReferences`

References

MetaCyc:OXIDATIVEPENT-PWY MetaCyc pentose phosphate pathway (oxidative branch) I (source version: 22.5)
RHEA:15841 Rhea glucose-6-phosphate dehydrogenase reaction (source version: 139)
RHEA:15842 Rhea 6-phospho-D-glucono-1,5-lactone-forming direction (source version: 139)
RHEA:12556 Rhea 6-phosphogluconolactonase reaction (source version: 139)
RHEA:12557 Rhea 6-phospho-D-gluconate-forming direction (source version: 139)
RHEA:10116 Rhea 6-phosphogluconate dehydrogenase reaction (source version: 139)
RHEA:10117 Rhea D-ribulose 5-phosphate-forming direction (source version: 139)
UniProtKB:P00350 UniProtKB:P00350 authority record (source version: 2026_03)
UniProtKB:P0AC53 UniProtKB:P0AC53 authority record (source version: 2026_03)
UniProtKB:P52697 UniProtKB:P52697 authority record (source version: 2026_03)

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 3 to 3; 0 directed-ID corrections; 3 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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