adenine and adenosine salvage III

MetaCyc:PWY-6609

The complete four-reaction route salvages adenine through adenosine, inosine and hypoxanthine to IMP in Escherichia coli K-12. The DeoD homohexamer forms adenosine from adenine and alpha-D-ribose 1-phosphate, Add deaminates adenosine, and DeoD then cleaves inosine. The Hpt homotetramer preferentially salvages hypoxanthine to IMP; Gpt also catalyzes this step with lower affinity for hypoxanthine than for its preferred guanine substrate. Historical genetic experiments used K-12 derivatives, while the native MetaCyc organism annotation is MG1655 and the reviewed proteins are assigned to K-12. The reversible phosphorylase reactions are oriented along the defined salvage route, without claiming that this flux dominates every growth condition. The graph ends at IMP; downstream AMP/GMP synthesis, direct AMP salvage and inosine kinase salvage are separate routes.

Pathway type

purine nucleotide salvage

Organism scope

Escherichia coli K-12 NCBITaxon:83333

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Pathway network

29 nodes · 42 asserted directed edges

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Chemical / cofactor
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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
Escherichia coli K-12 `NCBITaxon:83333`	taxon
water `CHEBI:15377`	small molecule
hydron `CHEBI:15378`	small molecule
adenosine `CHEBI:16335`	small molecule
adenine `CHEBI:16708`	small molecule
hypoxanthine `CHEBI:17368`	small molecule
inosine `CHEBI:17596`	small molecule
magnesium(2+) `CHEBI:18420`	cofactor
ammonium `CHEBI:28938`	small molecule
zinc(2+) `CHEBI:29105`	cofactor
diphosphate(3-) `CHEBI:33019`	small molecule
hydrogenphosphate `CHEBI:43474`	small molecule
alpha-D-ribose 1-phosphate(2-) `CHEBI:57720`	small molecule
5-O-phosphonato-alpha-D-ribofuranosyl diphosphate(5-) `CHEBI:58017`	small molecule
IMP(2-) `CHEBI:58053`	small molecule
Adenosine deaminase `UniProtKB:P22333`	protein
Purine nucleoside phosphorylase DeoD-type `UniProtKB:P0ABP8`	protein
Hypoxanthine phosphoribosyltransferase `UniProtKB:P0A9M2`	protein
Xanthine-guanine phosphoribosyltransferase `UniProtKB:P0A9M5`	protein
purine nucleoside phosphorylase `MetaCyc:DEOD-CPLX`	complex
hypoxanthine phosphoribosyltransferase `MetaCyc:CPLX0-7685`	complex
xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	complex
cytosol `GO:0005829`	cellular component
plasma membrane `GO:0005886`	cellular component
membrane `GO:0016020`	cellular component
alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	reaction	right to left
adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	reaction	left to right
inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	reaction	left to right
hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	reaction	right to left

Mechanistic edges

Mechanistic edges and their cited evidence
Subject	Predicate and description	Object	Evidence
alpha-D-ribose 1-phosphate(2-) `CHEBI:57720`	consumes	alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	RHEA:27644 Source assertion: RHEA:27644 explicitly lists CHEBI:57720 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27644 rh:substrates <http://rdf.rhea-db.org/27642_R>; <http://rdf.rhea-db.org/27642_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27642_compound_2276>; <http://rdf.rhea-db.org/Participant_27642_compound_2276> rh:compound <http://rdf.rhea-db.org/Compound_2276> / rh:chebi`
adenine `CHEBI:16708`	consumes	alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	RHEA:27644 Source assertion: RHEA:27644 explicitly lists CHEBI:16708 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27644 rh:substrates <http://rdf.rhea-db.org/27642_R>; <http://rdf.rhea-db.org/27642_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27642_compound_4174>; <http://rdf.rhea-db.org/Participant_27642_compound_4174> rh:compound <http://rdf.rhea-db.org/Compound_4174> / rh:chebi`
alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	produces	adenosine `CHEBI:16335`	RHEA:27644 Source assertion: RHEA:27644 explicitly lists CHEBI:16335 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27644 rh:products <http://rdf.rhea-db.org/27642_L>; <http://rdf.rhea-db.org/27642_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27642_compound_2547>; <http://rdf.rhea-db.org/Participant_27642_compound_2547> rh:compound <http://rdf.rhea-db.org/Compound_2547> / rh:chebi`
alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	produces	hydrogenphosphate `CHEBI:43474`	RHEA:27644 Source assertion: RHEA:27644 explicitly lists CHEBI:43474 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27644 rh:products <http://rdf.rhea-db.org/27642_L>; <http://rdf.rhea-db.org/27642_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27642_compound_5518>; <http://rdf.rhea-db.org/Participant_27642_compound_5518> rh:compound <http://rdf.rhea-db.org/Compound_5518> / rh:chebi`
adenosine `CHEBI:16335`	consumes	adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	RHEA:24409 Source assertion: RHEA:24409 explicitly lists CHEBI:16335 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:24409 rh:substrates <http://rdf.rhea-db.org/24408_L>; <http://rdf.rhea-db.org/24408_L> rh:contains1 <http://rdf.rhea-db.org/Participant_24408_compound_2547>; <http://rdf.rhea-db.org/Participant_24408_compound_2547> rh:compound <http://rdf.rhea-db.org/Compound_2547> / rh:chebi`
water `CHEBI:15377`	consumes	adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	RHEA:24409 Source assertion: RHEA:24409 explicitly lists CHEBI:15377 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:24409 rh:substrates <http://rdf.rhea-db.org/24408_L>; <http://rdf.rhea-db.org/24408_L> rh:contains1 <http://rdf.rhea-db.org/Participant_24408_compound_1283>; <http://rdf.rhea-db.org/Participant_24408_compound_1283> rh:compound <http://rdf.rhea-db.org/Compound_1283> / rh:chebi`
hydron `CHEBI:15378`	consumes	adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	RHEA:24409 Source assertion: RHEA:24409 explicitly lists CHEBI:15378 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:24409 rh:substrates <http://rdf.rhea-db.org/24408_L>; <http://rdf.rhea-db.org/24408_L> rh:contains1 <http://rdf.rhea-db.org/Participant_24408_compound_3249>; <http://rdf.rhea-db.org/Participant_24408_compound_3249> rh:compound <http://rdf.rhea-db.org/Compound_3249> / rh:chebi`
adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	produces	inosine `CHEBI:17596`	RHEA:24409 Source assertion: RHEA:24409 explicitly lists CHEBI:17596 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:24409 rh:products <http://rdf.rhea-db.org/24408_R>; <http://rdf.rhea-db.org/24408_R> rh:contains1 <http://rdf.rhea-db.org/Participant_24408_compound_1231>; <http://rdf.rhea-db.org/Participant_24408_compound_1231> rh:compound <http://rdf.rhea-db.org/Compound_1231> / rh:chebi`
adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	produces	ammonium `CHEBI:28938`	RHEA:24409 Source assertion: RHEA:24409 explicitly lists CHEBI:28938 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:24409 rh:products <http://rdf.rhea-db.org/24408_R>; <http://rdf.rhea-db.org/24408_R> rh:contains1 <http://rdf.rhea-db.org/Participant_24408_compound_1012>; <http://rdf.rhea-db.org/Participant_24408_compound_1012> rh:compound <http://rdf.rhea-db.org/Compound_1012> / rh:chebi`
inosine `CHEBI:17596`	consumes	inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	RHEA:27647 Source assertion: RHEA:27647 explicitly lists CHEBI:17596 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27647 rh:substrates <http://rdf.rhea-db.org/27646_L>; <http://rdf.rhea-db.org/27646_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27646_compound_1231>; <http://rdf.rhea-db.org/Participant_27646_compound_1231> rh:compound <http://rdf.rhea-db.org/Compound_1231> / rh:chebi`
hydrogenphosphate `CHEBI:43474`	consumes	inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	RHEA:27647 Source assertion: RHEA:27647 explicitly lists CHEBI:43474 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27647 rh:substrates <http://rdf.rhea-db.org/27646_L>; <http://rdf.rhea-db.org/27646_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27646_compound_5518>; <http://rdf.rhea-db.org/Participant_27646_compound_5518> rh:compound <http://rdf.rhea-db.org/Compound_5518> / rh:chebi`
inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	produces	alpha-D-ribose 1-phosphate(2-) `CHEBI:57720`	RHEA:27647 Source assertion: RHEA:27647 explicitly lists CHEBI:57720 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27647 rh:products <http://rdf.rhea-db.org/27646_R>; <http://rdf.rhea-db.org/27646_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27646_compound_2276>; <http://rdf.rhea-db.org/Participant_27646_compound_2276> rh:compound <http://rdf.rhea-db.org/Compound_2276> / rh:chebi`
inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	produces	hypoxanthine `CHEBI:17368`	RHEA:27647 Source assertion: RHEA:27647 explicitly lists CHEBI:17368 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27647 rh:products <http://rdf.rhea-db.org/27646_R>; <http://rdf.rhea-db.org/27646_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27646_compound_3881>; <http://rdf.rhea-db.org/Participant_27646_compound_3881> rh:compound <http://rdf.rhea-db.org/Compound_3881> / rh:chebi`
hypoxanthine `CHEBI:17368`	consumes	hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	RHEA:17975 Source assertion: RHEA:17975 explicitly lists CHEBI:17368 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:17975 rh:substrates <http://rdf.rhea-db.org/17973_R>; <http://rdf.rhea-db.org/17973_R> rh:contains1 <http://rdf.rhea-db.org/Participant_17973_compound_3881>; <http://rdf.rhea-db.org/Participant_17973_compound_3881> rh:compound <http://rdf.rhea-db.org/Compound_3881> / rh:chebi`
5-O-phosphonato-alpha-D-ribofuranosyl diphosphate(5-) `CHEBI:58017`	consumes	hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	RHEA:17975 Source assertion: RHEA:17975 explicitly lists CHEBI:58017 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:17975 rh:substrates <http://rdf.rhea-db.org/17973_R>; <http://rdf.rhea-db.org/17973_R> rh:contains1 <http://rdf.rhea-db.org/Participant_17973_compound_4203>; <http://rdf.rhea-db.org/Participant_17973_compound_4203> rh:compound <http://rdf.rhea-db.org/Compound_4203> / rh:chebi`
hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	produces	IMP(2-) `CHEBI:58053`	RHEA:17975 Source assertion: RHEA:17975 explicitly lists CHEBI:58053 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:17975 rh:products <http://rdf.rhea-db.org/17973_L>; <http://rdf.rhea-db.org/17973_L> rh:contains1 <http://rdf.rhea-db.org/Participant_17973_compound_1663>; <http://rdf.rhea-db.org/Participant_17973_compound_1663> rh:compound <http://rdf.rhea-db.org/Compound_1663> / rh:chebi`
hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	produces	diphosphate(3-) `CHEBI:33019`	RHEA:17975 Source assertion: RHEA:17975 explicitly lists CHEBI:33019 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:17975 rh:products <http://rdf.rhea-db.org/17973_L>; <http://rdf.rhea-db.org/17973_L> rh:contains1 <http://rdf.rhea-db.org/Participant_17973_compound_2106>; <http://rdf.rhea-db.org/Participant_17973_compound_2106> rh:compound <http://rdf.rhea-db.org/Compound_2106> / rh:chebi`
purine nucleoside phosphorylase `MetaCyc:DEOD-CPLX`	catalyzes DeoD catalyzes both phosphorylase steps. The first is run in the nucleoside-synthetic direction and the third in the phosphorolytic direction; no monomer sufficiency or universal net flux is implied.	alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	UniProtKB:P0ABP8 Source assertion: Reviewed DeoD catalytic-activity comment 4 assigns the matching Rhea reaction family with experimental PMID:235429 attribution. Comment 10 identifies a homohexamer; the enzyme catalyzes reversible phosphorolysis. Source location `comments[4].reaction; comments[4].reaction.evidences; comments[0]; comments[10]` MetaCyc:ADENPHOSPHOR-ENZRXN Source assertion: The native enzyme-reaction object connects DEOD-CPLX to this reaction and preserves its reversible catalytic scope. The pathway selects the salvage orientation. Source location `Enzymatic-Reaction[@frameid="ADENPHOSPHOR-ENZRXN"]/enzyme; reaction; reaction-direction` MetaCyc:PWY-6609 Source assertion: The four-step pathway selects adenine-to-adenosine synthesis for ADENPHOSPHOR-RXN and inosine-to-hypoxanthine cleavage for INOPHOSPHOR-RXN. Source location `Pathway[@frameid="PWY-6609"]/reaction-layout`
purine nucleoside phosphorylase `MetaCyc:DEOD-CPLX`	catalyzes DeoD catalyzes both phosphorylase steps. The first is run in the nucleoside-synthetic direction and the third in the phosphorolytic direction; no monomer sufficiency or universal net flux is implied.	inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	UniProtKB:P0ABP8 Source assertion: Reviewed DeoD catalytic-activity comment 3 assigns the matching Rhea reaction family with experimental PMID:235429 attribution. Comment 10 identifies a homohexamer; the enzyme catalyzes reversible phosphorolysis. Source location `comments[3].reaction; comments[3].reaction.evidences; comments[0]; comments[10]` MetaCyc:INOPHOSPHOR-ENZRXN Source assertion: The native enzyme-reaction object connects DEOD-CPLX to this reaction and preserves its reversible catalytic scope. The pathway selects the salvage orientation. Source location `Enzymatic-Reaction[@frameid="INOPHOSPHOR-ENZRXN"]/enzyme; reaction; reaction-direction` MetaCyc:PWY-6609 Source assertion: The four-step pathway selects adenine-to-adenosine synthesis for ADENPHOSPHOR-RXN and inosine-to-hypoxanthine cleavage for INOPHOSPHOR-RXN. Source location `Pathway[@frameid="PWY-6609"]/reaction-layout`
Adenosine deaminase `UniProtKB:P22333`	catalyzes	adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	UniProtKB:P22333 Source assertion: Reviewed catalytic-activity comment 1 assigns adenosine hydrolysis to RHEA:24408 and physiological left-to-right RHEA:24409, with experimental PMID:1998686 and PMID:357905 evidence alongside HAMAP inference. Source location `comments[1].reaction; comments[1].physiologicalReactions` MetaCyc:ADENODEAMIN-ENZRXN Source assertion: The native enzyme-reaction object assigns ADENODEAMIN-MONOMER to ADENODEAMIN-RXN. Source location `Enzymatic-Reaction[@frameid="ADENODEAMIN-ENZRXN"]/enzyme; reaction` MetaCyc:ADENODEAMIN-MONOMER Source assertion: The native E. coli entity explicitly cross-references P22333; its comment reports a 29 kDa apparent native mass from K-12 gel filtration, not a measured multimeric assembly. Source location `Protein[@frameid="ADENODEAMIN-MONOMER"]/dblink[dblink-db="UNIPROT"]; species; comment` PMID:765747 Source assertion: Adenosine deaminase activity was measured with adenosine, and Table 2 compares add mutants and an add+ transductant under histidine-supplemented conditions that block the alternate histidine-pathway route. Source location `pp. 86 and 88, Enzyme Assays/Adenosine Deaminase; Table 2 and footnotes`
hypoxanthine phosphoribosyltransferase `MetaCyc:CPLX0-7685`	catalyzes Hpt preferentially uses hypoxanthine; its role in IMP synthesis is a kinetic interpretation.	hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	UniProtKB:P0A9M2 Source assertion: Reviewed catalytic-activity comment 1 identifies RHEA:17973 and physiological right-to-left RHEA:17975. Hpt preferentially uses hypoxanthine; its role in IMP synthesis is a kinetic interpretation. Source location `comments[1].reaction; comments[1].physiologicalReactions; comments[0]` MetaCyc:HYPOXANPRIBOSYLTRAN-ENZRXN Source assertion: The native enzyme-reaction connects CPLX0-7685 to HYPOXANPRIBOSYLTRAN-RXN in its physiological nucleotide-forming direction. Source location `Enzymatic-Reaction[@frameid="HYPOXANPRIBOSYLTRAN-ENZRXN"]/enzyme; reaction; reaction-direction`
xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	catalyzes Gpt also accepts hypoxanthine, with lower affinity than guanine; this is not an equal-flux claim.	hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	UniProtKB:P0A9M5 Source assertion: Reviewed catalytic-activity comment 3 identifies RHEA:17973 and physiological right-to-left RHEA:17975. Gpt also accepts hypoxanthine, with lower affinity than guanine; this is not an equal-flux claim. Source location `comments[3].reaction; comments[3].physiologicalReactions; comments[0]` MetaCyc:HYPXPRIBOSYLTRAN-ENZRXN Source assertion: The native enzyme-reaction connects GPT-CPLX to HYPOXANPRIBOSYLTRAN-RXN in its physiological nucleotide-forming direction. Source location `Enzymatic-Reaction[@frameid="HYPXPRIBOSYLTRAN-ENZRXN"]/enzyme; reaction; reaction-direction`
Purine nucleoside phosphorylase DeoD-type `UniProtKB:P0ABP8`	part_of 6 copies per complex. Assembly composition does not make an isolated subunit an independently sufficient catalyst.	purine nucleoside phosphorylase `MetaCyc:DEOD-CPLX`	MetaCyc:DEOD-CPLX Source assertion: The native complex component slot specifies 6 copies of DEOD-MONOMER. Source location `Protein[@frameid="DEOD-CPLX"]/component/Protein; component/coefficient` MetaCyc:DEOD-MONOMER Source assertion: The native DEOD-MONOMER entity explicitly cross-references UniProt P0ABP8. Source location `Protein[@frameid="DEOD-MONOMER"]/dblink[dblink-db="UNIPROT"]` UniProtKB:P0ABP8 Source assertion: The reviewed SUBUNIT comment identifies the 6-subunit homooligomer and retains its original experimental citation evidence. Source location `comments[10].texts; comments[10].texts[0].evidences` PMID:30337572 Source assertion: All PNP structures in the study contain six identical 238-residue chains arranged as a trimer of dimers; the biochemical experiments use purified recombinant enzyme. Source location `BioC document/passage[40] (zero-based), Results and Discussion/Overall protein structures; passage[63], Methods/Preparation of ternary complexes for crystallisation`
Hypoxanthine phosphoribosyltransferase `UniProtKB:P0A9M2`	part_of 4 copies per complex. Assembly composition does not make an isolated subunit an independently sufficient catalyst.	hypoxanthine phosphoribosyltransferase `MetaCyc:CPLX0-7685`	MetaCyc:CPLX0-7685 Source assertion: The native complex component slot specifies 4 copies of HYPOXANPRIBOSYLTRAN-MONOMER. Source location `Protein[@frameid="CPLX0-7685"]/component/Protein; component/coefficient` MetaCyc:HYPOXANPRIBOSYLTRAN-MONOMER Source assertion: The native HYPOXANPRIBOSYLTRAN-MONOMER entity explicitly cross-references UniProt P0A9M2. Source location `Protein[@frameid="HYPOXANPRIBOSYLTRAN-MONOMER"]/dblink[dblink-db="UNIPROT"]` UniProtKB:P0A9M2 Source assertion: The reviewed SUBUNIT comment identifies the 4-subunit homooligomer and retains its original experimental citation evidence. Source location `comments[7].texts; comments[7].texts[0].evidences`
Xanthine-guanine phosphoribosyltransferase `UniProtKB:P0A9M5`	part_of 4 copies per complex. The earlier apparent trimer was superseded by later structural evidence for a tetramer.	xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	MetaCyc:GPT-CPLX Source assertion: The native complex component slot specifies 4 copies of GPT-MONOMER. Source location `Protein[@frameid="GPT-CPLX"]/component/Protein; component/coefficient` MetaCyc:GPT-MONOMER Source assertion: The native GPT-MONOMER entity explicitly cross-references UniProt P0A9M5. Source location `Protein[@frameid="GPT-MONOMER"]/dblink[dblink-db="UNIPROT"]` UniProtKB:P0A9M5 Source assertion: The reviewed SUBUNIT comment identifies the 4-subunit homooligomer and retains its original experimental citation evidence. Source location `comments[9].texts; comments[9].texts[0].evidences` PMID:9100006 Source assertion: The primary abstract identifies E. coli XPRT as a tetramer and describes hypoxanthine as a substrate yielding IMP. Source location `resultList.result[id="9100006"].abstractText` PMID:6305942 Source assertion: An earlier gel-filtration study reported trimeric behavior. The graph uses the later tetramer supported by current reviewed annotation and structural studies; the historical discrepancy remains explicit. Source location `resultList.result[id="6305942"].abstractText`
Adenosine deaminase `UniProtKB:P22333`	has_cofactor The zinc assignment is explicitly inferred by HAMAP; the inspected K-12 genetic study does not establish zinc binding or stoichiometry.	zinc(2+) `CHEBI:29105`	UniProtKB:P22333 Source assertion: The reviewed cofactor annotation assigns Zn(2+) and one zinc per subunit through ECO:0000255, HAMAP-Rule MF_00540. This is a similarity-based assignment, not a direct E. coli metal-binding experiment. Source location `comments[3].cofactors; comments[3].note`
hypoxanthine phosphoribosyltransferase `MetaCyc:CPLX0-7685`	has_cofactor Metal requirement and structural observation are distinguished from a fixed per-complex metal stoichiometry, which is not asserted.	magnesium(2+) `CHEBI:18420`	UniProtKB:P0A9M2 Source assertion: The reviewed magnesium cofactor annotation is ECO:0000305, based on PMID:12070315; the SUBUNIT comment identifies a homotetramer. Source location `comments[3].cofactors; comments[7]` PMID:12070315 Source assertion: The primary abstract describes a divalent-metal requirement, usually magnesium in vivo, and observes Mg(2+) bound to Glu103/Asp104 in the free E. coli Hpt structure. Source location `resultList.result[id="12070315"].abstractText`
xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	has_cofactor	magnesium(2+) `CHEBI:18420`	UniProtKB:P0A9M5 Source assertion: The reviewed cofactor annotation assigns Mg(2+) with ECO:0000269 attribution to PMID:9100006. Source location `comments[4].cofactors` PMID:9100006 Source assertion: The primary abstract reports a magnesium ion at the PRib-PP binding site, interacting with Asp89. Source location `resultList.result[id="9100006"].abstractText`
IMP(2-) `CHEBI:58053`	inhibits This records the curated enzyme-level product inhibition; no concentration threshold or cellular regulatory strength is inferred.	hypoxanthine phosphoribosyltransferase `MetaCyc:CPLX0-7685`	UniProtKB:P0A9M2 Source assertion: The reviewed activity-regulation comment states inhibition by the product IMP, with ECO:0000269 attribution to PMID:12070315. Source location `comments[4].texts[0]; comments[4].texts[0].evidences`
Adenosine deaminase `UniProtKB:P22333`	located_in	cytosol `GO:0005829`	UniProtKB:P22333 Source assertion: The inspected protein record has a GO:0005829 cytosol cross-reference with IDA:EcoCyc attribution. This is the database localization assertion; exclusivity is not implied. Source location `uniProtKBCrossReferences[database="GO",id="GO:0005829"].properties`
Purine nucleoside phosphorylase DeoD-type `UniProtKB:P0ABP8`	located_in	cytosol `GO:0005829`	UniProtKB:P0ABP8 Source assertion: The inspected protein record has a GO:0005829 cytosol cross-reference with IDA:EcoCyc attribution. This is the database localization assertion; exclusivity is not implied. Source location `uniProtKBCrossReferences[database="GO",id="GO:0005829"].properties`
Hypoxanthine phosphoribosyltransferase `UniProtKB:P0A9M2`	located_in	cytosol `GO:0005829`	UniProtKB:P0A9M2 Source assertion: The inspected protein record has a GO:0005829 cytosol cross-reference with IDA:EcoCyc attribution. This is the database localization assertion; exclusivity is not implied. Source location `uniProtKBCrossReferences[database="GO",id="GO:0005829"].properties`
Xanthine-guanine phosphoribosyltransferase `UniProtKB:P0A9M5`	located_in	cytosol `GO:0005829`	UniProtKB:P0A9M5 Source assertion: The inspected protein record has a GO:0005829 cytosol cross-reference with IDA:EcoCyc attribution. This is the database localization assertion; exclusivity is not implied. Source location `uniProtKBCrossReferences[database="GO",id="GO:0005829"].properties`
Purine nucleoside phosphorylase DeoD-type `UniProtKB:P0ABP8`	located_in This source-specific localization evidence is retained with its evidence tier; it does not move the whole pathway into this compartment.	membrane `GO:0016020`	UniProtKB:P0ABP8 Source assertion: The inspected protein record also has a GO:0016020 localization cross-reference with HDA:UniProtKB attribution, alongside its cytosol annotation. The annotations do not establish exclusive localization. Source location `uniProtKBCrossReferences[database="GO",id="GO:0016020"].properties`
Xanthine-guanine phosphoribosyltransferase `UniProtKB:P0A9M5`	located_in This source-specific localization evidence is retained with its evidence tier; it does not move the whole pathway into this compartment.	plasma membrane `GO:0005886`	UniProtKB:P0A9M5 Source assertion: The inspected protein record also has a GO:0005886 localization cross-reference with IEA:UniProtKB-SubCell attribution, alongside its cytosol annotation. The annotations do not establish exclusive localization. Source location `uniProtKBCrossReferences[database="GO",id="GO:0005886"].properties`
alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	part_of	`MetaCyc:PWY-6609`	MetaCyc:PWY-6609 Source assertion: The native complete pathway includes ADENPHOSPHOR-RXN; its reaction-layout selects the orientation used here. Source location `Pathway[@frameid="PWY-6609"]/reaction-list; reaction-layout` MetaCyc:ADENPHOSPHOR-RXN Source assertion: Native ADENPHOSPHOR-RXN has Rhea cross-reference 27645. Its chemical roles match the selected Rhea family; protonation is retained from exact Rhea species rather than asserted as an exactMatch between differing source chemical forms. Source location `Reaction[@frameid="ADENPHOSPHOR-RXN"]/dblink[dblink-db="RHEA"]; left; right; reaction-direction` RHEA:27644 Source assertion: Rhea master 27642 explicitly links directional member 27644 and bidirectional member 27645. Source location `rhea.rdf.gz; rh:27642 rh:directionalReaction rh:27644; rh:27642 rh:bidirectionalReaction rh:27645`
adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	part_of	`MetaCyc:PWY-6609`	MetaCyc:PWY-6609 Source assertion: The native complete pathway includes ADENODEAMIN-RXN; its reaction-layout selects the orientation used here. Source location `Pathway[@frameid="PWY-6609"]/reaction-list; reaction-layout` MetaCyc:ADENODEAMIN-RXN Source assertion: Native ADENODEAMIN-RXN has Rhea cross-reference 24408. Its chemical roles match the selected Rhea family; protonation is retained from exact Rhea species rather than asserted as an exactMatch between differing source chemical forms. Source location `Reaction[@frameid="ADENODEAMIN-RXN"]/dblink[dblink-db="RHEA"]; left; right; reaction-direction` RHEA:24409 Source assertion: Rhea master 24408 explicitly links directional member 24409. Source location `rhea.rdf.gz; rh:24408 rh:directionalReaction rh:24409`
inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	part_of	`MetaCyc:PWY-6609`	MetaCyc:PWY-6609 Source assertion: The native complete pathway includes INOPHOSPHOR-RXN; its reaction-layout selects the orientation used here. Source location `Pathway[@frameid="PWY-6609"]/reaction-list; reaction-layout` MetaCyc:INOPHOSPHOR-RXN Source assertion: Native INOPHOSPHOR-RXN has Rhea cross-reference 27649. Its chemical roles match the selected Rhea family; protonation is retained from exact Rhea species rather than asserted as an exactMatch between differing source chemical forms. Source location `Reaction[@frameid="INOPHOSPHOR-RXN"]/dblink[dblink-db="RHEA"]; left; right; reaction-direction` RHEA:27647 Source assertion: Rhea master 27646 explicitly links directional member 27647 and bidirectional member 27649. Source location `rhea.rdf.gz; rh:27646 rh:directionalReaction rh:27647; rh:27646 rh:bidirectionalReaction rh:27649`
hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	part_of	`MetaCyc:PWY-6609`	MetaCyc:PWY-6609 Source assertion: The native complete pathway includes HYPOXANPRIBOSYLTRAN-RXN; its reaction-layout selects the orientation used here. Source location `Pathway[@frameid="PWY-6609"]/reaction-list; reaction-layout` MetaCyc:HYPOXANPRIBOSYLTRAN-RXN Source assertion: Native HYPOXANPRIBOSYLTRAN-RXN has Rhea cross-reference 17973. Its chemical roles match the selected Rhea family; protonation is retained from exact Rhea species rather than asserted as an exactMatch between differing source chemical forms. Source location `Reaction[@frameid="HYPOXANPRIBOSYLTRAN-RXN"]/dblink[dblink-db="RHEA"]; left; right; reaction-direction` RHEA:17975 Source assertion: Rhea master 17973 explicitly links directional member 17975. Source location `rhea.rdf.gz; rh:17973 rh:directionalReaction rh:17975`
alpha-D-ribose 1-phosphate + adenine => adenosine + phosphate `RHEA:27644`	provides_input_for The shared metabolite supplies the next reaction. This is material connectivity, not a claim of direct enzyme channeling or exclusive flux.	adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	MetaCyc:PWY-6609 Source assertion: The pathway lists ADENPHOSPHOR-RXN as the predecessor of ADENODEAMIN-RXN. Source location `Pathway[@frameid="PWY-6609"]/reaction-ordering[Reaction/@frameid="ADENODEAMIN-RXN"]` PMID:765747 Source assertion: Figure 1 places purine nucleoside phosphorylase and adenosine deaminase between adenine, adenosine, inosine and hypoxanthine, with phosphoribosyltransferases forming IMP. Table 1 identifies K-12-derived strains; the figure also depicts distinct alternative routes. Source location `p. 85 Figure 1 and caption; p. 87 Table 1; p. 90 Figure 3 caption` RHEA:27644 Source assertion: RHEA:27644 explicitly lists CHEBI:16335 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27644 rh:products <http://rdf.rhea-db.org/27642_L>; <http://rdf.rhea-db.org/27642_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27642_compound_2547>; <http://rdf.rhea-db.org/Participant_27642_compound_2547> rh:compound <http://rdf.rhea-db.org/Compound_2547> / rh:chebi` RHEA:24409 Source assertion: RHEA:24409 explicitly lists CHEBI:16335 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:24409 rh:substrates <http://rdf.rhea-db.org/24408_L>; <http://rdf.rhea-db.org/24408_L> rh:contains1 <http://rdf.rhea-db.org/Participant_24408_compound_2547>; <http://rdf.rhea-db.org/Participant_24408_compound_2547> rh:compound <http://rdf.rhea-db.org/Compound_2547> / rh:chebi`
adenosine + H2O + H(+) => inosine + NH4(+) `RHEA:24409`	provides_input_for The shared metabolite supplies the next reaction. This is material connectivity, not a claim of direct enzyme channeling or exclusive flux.	inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	MetaCyc:PWY-6609 Source assertion: The pathway lists ADENODEAMIN-RXN as the predecessor of INOPHOSPHOR-RXN. Source location `Pathway[@frameid="PWY-6609"]/reaction-ordering[Reaction/@frameid="INOPHOSPHOR-RXN"]` PMID:765747 Source assertion: Figure 1 places purine nucleoside phosphorylase and adenosine deaminase between adenine, adenosine, inosine and hypoxanthine, with phosphoribosyltransferases forming IMP. Table 1 identifies K-12-derived strains; the figure also depicts distinct alternative routes. Source location `p. 85 Figure 1 and caption; p. 87 Table 1; p. 90 Figure 3 caption` RHEA:24409 Source assertion: RHEA:24409 explicitly lists CHEBI:17596 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:24409 rh:products <http://rdf.rhea-db.org/24408_R>; <http://rdf.rhea-db.org/24408_R> rh:contains1 <http://rdf.rhea-db.org/Participant_24408_compound_1231>; <http://rdf.rhea-db.org/Participant_24408_compound_1231> rh:compound <http://rdf.rhea-db.org/Compound_1231> / rh:chebi` RHEA:27647 Source assertion: RHEA:27647 explicitly lists CHEBI:17596 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27647 rh:substrates <http://rdf.rhea-db.org/27646_L>; <http://rdf.rhea-db.org/27646_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27646_compound_1231>; <http://rdf.rhea-db.org/Participant_27646_compound_1231> rh:compound <http://rdf.rhea-db.org/Compound_1231> / rh:chebi`
inosine + phosphate => alpha-D-ribose 1-phosphate + hypoxanthine `RHEA:27647`	provides_input_for The shared metabolite supplies the next reaction. This is material connectivity, not a claim of direct enzyme channeling or exclusive flux.	hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate => IMP + diphosphate `RHEA:17975`	MetaCyc:PWY-6609 Source assertion: The pathway lists INOPHOSPHOR-RXN as the predecessor of HYPOXANPRIBOSYLTRAN-RXN. Source location `Pathway[@frameid="PWY-6609"]/reaction-ordering[Reaction/@frameid="HYPOXANPRIBOSYLTRAN-RXN"]` PMID:765747 Source assertion: Figure 1 places purine nucleoside phosphorylase and adenosine deaminase between adenine, adenosine, inosine and hypoxanthine, with phosphoribosyltransferases forming IMP. Table 1 identifies K-12-derived strains; the figure also depicts distinct alternative routes. Source location `p. 85 Figure 1 and caption; p. 87 Table 1; p. 90 Figure 3 caption` RHEA:27647 Source assertion: RHEA:27647 explicitly lists CHEBI:17368 as a product with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:27647 rh:products <http://rdf.rhea-db.org/27646_R>; <http://rdf.rhea-db.org/27646_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27646_compound_3881>; <http://rdf.rhea-db.org/Participant_27646_compound_3881> rh:compound <http://rdf.rhea-db.org/Compound_3881> / rh:chebi` RHEA:17975 Source assertion: RHEA:17975 explicitly lists CHEBI:17368 as a substrate with coefficient 1. Formula and charge are those of the linked Rhea compound and ChEBI species. Source location `rhea.rdf.gz; rh:17975 rh:substrates <http://rdf.rhea-db.org/17973_R>; <http://rdf.rhea-db.org/17973_R> rh:contains1 <http://rdf.rhea-db.org/Participant_17973_compound_3881>; <http://rdf.rhea-db.org/Participant_17973_compound_3881> rh:compound <http://rdf.rhea-db.org/Compound_3881> / rh:chebi`

References

MetaCyc:ADENODEAMIN-ENZRXN MetaCyc native ADENODEAMIN-ENZRXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:ADENODEAMIN-MONOMER MetaCyc native ADENODEAMIN-MONOMER (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:ADENODEAMIN-RXN MetaCyc native ADENODEAMIN-RXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:ADENPHOSPHOR-ENZRXN MetaCyc native ADENPHOSPHOR-ENZRXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:ADENPHOSPHOR-RXN MetaCyc native ADENPHOSPHOR-RXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:CPLX0-7685 MetaCyc native CPLX0-7685 (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:DEOD-CPLX MetaCyc native DEOD-CPLX (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:DEOD-MONOMER MetaCyc native DEOD-MONOMER (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:GPT-CPLX MetaCyc native GPT-CPLX (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:GPT-MONOMER MetaCyc native GPT-MONOMER (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:HYPOXANPRIBOSYLTRAN-ENZRXN MetaCyc native HYPOXANPRIBOSYLTRAN-ENZRXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:HYPOXANPRIBOSYLTRAN-MONOMER MetaCyc native HYPOXANPRIBOSYLTRAN-MONOMER (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:HYPOXANPRIBOSYLTRAN-RXN MetaCyc native HYPOXANPRIBOSYLTRAN-RXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:HYPXPRIBOSYLTRAN-ENZRXN MetaCyc native HYPXPRIBOSYLTRAN-ENZRXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:INOPHOSPHOR-ENZRXN MetaCyc native INOPHOSPHOR-ENZRXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:INOPHOSPHOR-RXN MetaCyc native INOPHOSPHOR-RXN (source version: MetaCyc 22.5 public SGD-hosted native XML)
MetaCyc:PWY-6609 MetaCyc native PWY-6609 (source version: MetaCyc 22.5 public SGD-hosted native XML)
PMID:12070315 Crystal structures of free, IMP-, and GMP-bound Escherichia coli hypoxanthine phosphoribosyltransferase. (source version: Primary abstract in Europe PMC core batch response; digest covers complete JSON batch)
PMID:30337572 Crystallographic snapshots of ligand binding to hexameric purine nucleoside phosphorylase and kinetic studies give insight into the mechanism of catalysis. (source version: Primary full text in NCBI BioC XML; digest covers complete response)
PMID:6305942 Purification and characterization of Escherichia coli guanine-xanthine phosphoribosyltransferase produced by a high efficiency expression plasmid utilizing a lambda PL promoter and CI857 temperature-sensitive repressor. (source version: Primary abstract in Europe PMC core batch response; digest covers complete JSON batch)
PMID:765747 Location on the chromosome of Escherichia coli of genes governing purine metabolism. Adenosine deaminase (add), guanosine kinase (gsk) and hypoxanthine phosphoribosyltransferase (hpt). (source version: Primary full PDF; digest covers original seven-page article)
PMID:9100006 Crystal structure of Escherichia coli xanthine phosphoribosyltransferase. (source version: Primary abstract in Europe PMC core batch response; digest covers complete JSON batch)
RHEA:17975 Rhea directed reaction 17975 (source version: Rhea release 142; SHA256 covers complete original RDF gzip)
RHEA:24409 Rhea directed reaction 24409 (source version: Rhea release 142; SHA256 covers complete original RDF gzip)
RHEA:27644 Rhea directed reaction 27644 (source version: Rhea release 142; SHA256 covers complete original RDF gzip)
RHEA:27647 Rhea directed reaction 27647 (source version: Rhea release 142; SHA256 covers complete original RDF gzip)
UniProtKB:P0A9M2 Reviewed UniProtKB P0A9M2 (source version: UniProt release 2026_03; response release date 02-September-2026)
UniProtKB:P0A9M5 Reviewed UniProtKB P0A9M5 (source version: UniProt release 2026_03; response release date 02-September-2026)
UniProtKB:P0ABP8 Reviewed UniProtKB P0ABP8 (source version: UniProt release 2026_03; response release date 02-September-2026)
UniProtKB:P22333 Reviewed UniProtKB P22333 (source version: UniProt release 2026_03; response release date 02-September-2026)

Curation history

2026-10-11T04:37:05Z Codex
- CREATE — Add the complete four-reaction adenine and adenosine salvage III route.
  Retain the exact MetaCyc boundary through IMP, Hpt/Gpt specificity, source-specific assembly/cofactor tiers and historical experimental scope. Exact source dossiers and author checks are in research/pathway_additions/2026-10-11-next-189. Independent scientific reviews and shared validation are recorded separately.
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2026-10-11T04:47:14Z Codex
- EDIT — Separate native pathway ordering from Rhea intermediate identity evidence
  Corrected the three ordering-edge source assertions to describe only native MetaCyc ordering and attached six exact Rhea participant-side identity assertions for the shared intermediates. The four reactions, 42 edges and biological scope are preserved. Independent initial review 20261011T044538Z-adenine-salvage-initial-independent-review remains immutable; final source replay and successor review are recorded separately.
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