superpathway of guanine and guanosine salvage

MetaCyc:PWY-6579

The complete three-reaction superpathway salvages guanosine and guanine to GMP in Escherichia coli K-12 MG1655. It combines direct ATP-dependent guanosine phosphorylation by Gsk with guanosine phosphorolysis by the DeoD homohexamer followed by Gpt-dependent phosphoribosyl transfer to guanine. The two branches converge on GMP. Native MG1655 annotations are supported by reviewed K-12 proteins and inspected enzyme studies; the 2020 Gsk regulation experiments used MG1655-derived strains. Gsk is an active dimer under the examined inhibitor-free conditions, while GDP and ppGpp promote tetramerization; ppGpp-bound tetramers are less active than ppGpp-bound dimers. Gpt is represented by the later experimentally supported homotetramer. Each branch retains the complete charge- and stereochemistry-resolved reaction sides; its direction describes orientation relative to the Rhea master reaction.

Pathway type

purine nucleotide salvage

Organism scope

Escherichia coli str. K-12 substr. MG1655 NCBITaxon:511145

Read the source YAML

Pathway network

23 nodes · 27 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
Protein / complex
Pathway
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
Escherichia coli str. K-12 substr. MG1655 `NCBITaxon:511145`	taxon
guanosine `CHEBI:16750`	small molecule
ATP(4-) `CHEBI:30616`	small molecule
guanosine 5'-monophosphate(2-) `CHEBI:58115`	small molecule
ADP(3-) `CHEBI:456216`	small molecule
hydron `CHEBI:15378`	small molecule
hydrogenphosphate `CHEBI:43474`	small molecule
alpha-D-ribose 1-phosphate(2-) `CHEBI:57720`	small molecule
guanine `CHEBI:16235`	small molecule
5-O-phosphonato-alpha-D-ribofuranosyl diphosphate(5-) `CHEBI:58017`	small molecule
diphosphate(3-) `CHEBI:33019`	small molecule
magnesium(2+) `CHEBI:18420`	cofactor
GDP(3-) `CHEBI:58189`	small molecule
guanosine 3',5'-bis(diphosphate)(5-) `CHEBI:77828`	small molecule
Guanosine-inosine kinase `UniProtKB:P0AEW6`	protein
Purine nucleoside phosphorylase DeoD-type `UniProtKB:P0ABP8`	protein
Xanthine-guanine phosphoribosyltransferase `UniProtKB:P0A9M5`	protein
inosine/guanosine kinase `MetaCyc:CPLX0-322`	complex
purine nucleoside phosphorylase `MetaCyc:DEOD-CPLX`	complex
xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	complex
guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	reaction	left to right
guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	reaction	left to right
guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	reaction	right to left

Mechanistic edges

Mechanistic edges and their cited evidence
Subject	Predicate and description	Object	Evidence
guanosine `CHEBI:16750`	consumes	guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	RHEA:27711 Source assertion: RHEA:27711 explicitly lists CHEBI:16750 on its substrates side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:27711 rh:substrates <http://rdf.rhea-db.org/27710_L>; <http://rdf.rhea-db.org/27710_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27710_compound_1817>; <http://rdf.rhea-db.org/Participant_27710_compound_1817> rh:compound <http://rdf.rhea-db.org/Compound_1817> / rh:chebi`
ATP(4-) `CHEBI:30616`	consumes	guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	RHEA:27711 Source assertion: RHEA:27711 explicitly lists CHEBI:30616 on its substrates side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:27711 rh:substrates <http://rdf.rhea-db.org/27710_L>; <http://rdf.rhea-db.org/27710_L> rh:contains1 <http://rdf.rhea-db.org/Participant_27710_compound_6372>; <http://rdf.rhea-db.org/Participant_27710_compound_6372> rh:compound <http://rdf.rhea-db.org/Compound_6372> / rh:chebi`
guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	produces	guanosine 5'-monophosphate(2-) `CHEBI:58115`	RHEA:27711 Source assertion: RHEA:27711 explicitly lists CHEBI:58115 on its products side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:27711 rh:products <http://rdf.rhea-db.org/27710_R>; <http://rdf.rhea-db.org/27710_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27710_compound_3807>; <http://rdf.rhea-db.org/Participant_27710_compound_3807> rh:compound <http://rdf.rhea-db.org/Compound_3807> / rh:chebi`
guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	produces	ADP(3-) `CHEBI:456216`	RHEA:27711 Source assertion: RHEA:27711 explicitly lists CHEBI:456216 on its products side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:27711 rh:products <http://rdf.rhea-db.org/27710_R>; <http://rdf.rhea-db.org/27710_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27710_compound_2710>; <http://rdf.rhea-db.org/Participant_27710_compound_2710> rh:compound <http://rdf.rhea-db.org/Compound_2710> / rh:chebi`
guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	produces	hydron `CHEBI:15378`	RHEA:27711 Source assertion: RHEA:27711 explicitly lists CHEBI:15378 on its products side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:27711 rh:products <http://rdf.rhea-db.org/27710_R>; <http://rdf.rhea-db.org/27710_R> rh:contains1 <http://rdf.rhea-db.org/Participant_27710_compound_3249>; <http://rdf.rhea-db.org/Participant_27710_compound_3249> rh:compound <http://rdf.rhea-db.org/Compound_3249> / rh:chebi`
guanosine `CHEBI:16750`	consumes	guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	RHEA:13234 Source assertion: RHEA:13234 explicitly lists CHEBI:16750 on its substrates side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:13234 rh:substrates <http://rdf.rhea-db.org/13233_L>; <http://rdf.rhea-db.org/13233_L> rh:contains1 <http://rdf.rhea-db.org/Participant_13233_compound_1817>; <http://rdf.rhea-db.org/Participant_13233_compound_1817> rh:compound <http://rdf.rhea-db.org/Compound_1817> / rh:chebi`
hydrogenphosphate `CHEBI:43474`	consumes	guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	RHEA:13234 Source assertion: RHEA:13234 explicitly lists CHEBI:43474 on its substrates side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:13234 rh:substrates <http://rdf.rhea-db.org/13233_L>; <http://rdf.rhea-db.org/13233_L> rh:contains1 <http://rdf.rhea-db.org/Participant_13233_compound_5518>; <http://rdf.rhea-db.org/Participant_13233_compound_5518> rh:compound <http://rdf.rhea-db.org/Compound_5518> / rh:chebi`
guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	produces	alpha-D-ribose 1-phosphate(2-) `CHEBI:57720`	RHEA:13234 Source assertion: RHEA:13234 explicitly lists CHEBI:57720 on its products side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:13234 rh:products <http://rdf.rhea-db.org/13233_R>; <http://rdf.rhea-db.org/13233_R> rh:contains1 <http://rdf.rhea-db.org/Participant_13233_compound_2276>; <http://rdf.rhea-db.org/Participant_13233_compound_2276> rh:compound <http://rdf.rhea-db.org/Compound_2276> / rh:chebi`
guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	produces	guanine `CHEBI:16235`	RHEA:13234 Source assertion: RHEA:13234 explicitly lists CHEBI:16235 on its products side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:13234 rh:products <http://rdf.rhea-db.org/13233_R>; <http://rdf.rhea-db.org/13233_R> rh:contains1 <http://rdf.rhea-db.org/Participant_13233_compound_2523>; <http://rdf.rhea-db.org/Participant_13233_compound_2523> rh:compound <http://rdf.rhea-db.org/Compound_2523> / rh:chebi`
guanine `CHEBI:16235`	consumes	guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	RHEA:25426 Source assertion: RHEA:25426 explicitly lists CHEBI:16235 on its substrates side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:25426 rh:substrates <http://rdf.rhea-db.org/25424_R>; <http://rdf.rhea-db.org/25424_R> rh:contains1 <http://rdf.rhea-db.org/Participant_25424_compound_2523>; <http://rdf.rhea-db.org/Participant_25424_compound_2523> rh:compound <http://rdf.rhea-db.org/Compound_2523> / rh:chebi`
5-O-phosphonato-alpha-D-ribofuranosyl diphosphate(5-) `CHEBI:58017`	consumes	guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	RHEA:25426 Source assertion: RHEA:25426 explicitly lists CHEBI:58017 on its substrates side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:25426 rh:substrates <http://rdf.rhea-db.org/25424_R>; <http://rdf.rhea-db.org/25424_R> rh:contains1 <http://rdf.rhea-db.org/Participant_25424_compound_4203>; <http://rdf.rhea-db.org/Participant_25424_compound_4203> rh:compound <http://rdf.rhea-db.org/Compound_4203> / rh:chebi`
guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	produces	guanosine 5'-monophosphate(2-) `CHEBI:58115`	RHEA:25426 Source assertion: RHEA:25426 explicitly lists CHEBI:58115 on its products side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:25426 rh:products <http://rdf.rhea-db.org/25424_L>; <http://rdf.rhea-db.org/25424_L> rh:contains1 <http://rdf.rhea-db.org/Participant_25424_compound_3807>; <http://rdf.rhea-db.org/Participant_25424_compound_3807> rh:compound <http://rdf.rhea-db.org/Compound_3807> / rh:chebi`
guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	produces	diphosphate(3-) `CHEBI:33019`	RHEA:25426 Source assertion: RHEA:25426 explicitly lists CHEBI:33019 on its products side with coefficient 1; exact formula and charge follow the linked Rhea compound and ChEBI. Source location `rhea.rdf.gz; rh:25426 rh:products <http://rdf.rhea-db.org/25424_L>; <http://rdf.rhea-db.org/25424_L> rh:contains1 <http://rdf.rhea-db.org/Participant_25424_compound_2106>; <http://rdf.rhea-db.org/Participant_25424_compound_2106> rh:compound <http://rdf.rhea-db.org/Compound_2106> / rh:chebi`
guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	part_of	`MetaCyc:PWY-6579`	MetaCyc:PWY-6579 Source assertion: PWY-6579 explicitly includes PWY-6618 as a constituent pathway. Its complete native constituent list is PWY-6618 and PWY-6620; the separately cited subpathway records supply their reaction membership. Source location `PWY-6579.xml /ptools-xml/Pathway[@frameid="PWY-6579"]/reaction-list/Pathway[@frameid="PWY-6618"]` MetaCyc:PWY-6618 Source assertion: PWY-6618 explicitly contains GUANOSINEKIN-RXN in its reaction-list. This is explicit native pathway membership. Source location `PWY-6618.xml /ptools-xml/Pathway/reaction-list/Reaction[@frameid="GUANOSINEKIN-RXN"]` MetaCyc:GUANOSINEKIN-RXN Source assertion: GUANOSINEKIN-RXN supplies explicit native chemical sides and links Rhea member 27711. Native orientation is PHYSIOL-LEFT-TO-RIGHT. Source location `GUANOSINEKIN-RXN.xml /ptools-xml/Reaction/(left\|right\|reaction-direction\|dblink[dblink-db="RHEA"])` RHEA:27711 Source assertion: Rhea master 27710 links directional member 27711; its left-to-right member has the complete selected substrate/product sides. Native and Rhea members are reconciled through this inspected family. Source location `rhea.rdf.gz; rh:27710 rh:directionalReaction rh:27711; rh:27710 rh:bidirectionalReaction; rh:27711 rh:substrates/rh:products/rh:equation`
guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	part_of	`MetaCyc:PWY-6579`	MetaCyc:PWY-6579 Source assertion: PWY-6579 explicitly includes PWY-6620 as a constituent pathway. Its complete native constituent list is PWY-6618 and PWY-6620; the separately cited subpathway records supply their reaction membership. Source location `PWY-6579.xml /ptools-xml/Pathway[@frameid="PWY-6579"]/reaction-list/Pathway[@frameid="PWY-6620"]` MetaCyc:PWY-6620 Source assertion: PWY-6620 explicitly contains RXN0-5199 in its reaction-list. This is explicit native pathway membership. Source location `PWY-6620.xml /ptools-xml/Pathway/reaction-list/Reaction[@frameid="RXN0-5199"]` MetaCyc:RXN0-5199 Source assertion: RXN0-5199 supplies explicit native chemical sides and links Rhea member 13236. Native orientation is REVERSIBLE. Source location `RXN0-5199.xml /ptools-xml/Reaction/(left\|right\|reaction-direction\|dblink[dblink-db="RHEA"])` RHEA:13234 Source assertion: Rhea master 13233 links directional member 13234; its left-to-right member has the complete selected substrate/product sides. Native and Rhea members are reconciled through this inspected family. Source location `rhea.rdf.gz; rh:13233 rh:directionalReaction rh:13234; rh:13233 rh:bidirectionalReaction; rh:13234 rh:substrates/rh:products/rh:equation`
guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	part_of	`MetaCyc:PWY-6579`	MetaCyc:PWY-6579 Source assertion: PWY-6579 explicitly includes PWY-6620 as a constituent pathway. Its complete native constituent list is PWY-6618 and PWY-6620; the separately cited subpathway records supply their reaction membership. Source location `PWY-6579.xml /ptools-xml/Pathway[@frameid="PWY-6579"]/reaction-list/Pathway[@frameid="PWY-6620"]` MetaCyc:PWY-6620 Source assertion: PWY-6620 explicitly contains GUANPRIBOSYLTRAN-RXN in its reaction-list. This is explicit native pathway membership. Source location `PWY-6620.xml /ptools-xml/Pathway/reaction-list/Reaction[@frameid="GUANPRIBOSYLTRAN-RXN"]` MetaCyc:GUANPRIBOSYLTRAN-RXN Source assertion: GUANPRIBOSYLTRAN-RXN supplies explicit native chemical sides and links Rhea member 25427. Native orientation is PHYSIOL-RIGHT-TO-LEFT. Source location `GUANPRIBOSYLTRAN-RXN.xml /ptools-xml/Reaction/(left\|right\|reaction-direction\|dblink[dblink-db="RHEA"])` RHEA:25426 Source assertion: Rhea master 25424 links directional member 25426; its right-to-left member has the complete selected substrate/product sides. Native and Rhea members are reconciled through this inspected family. Source location `rhea.rdf.gz; rh:25424 rh:directionalReaction rh:25426; rh:25424 rh:bidirectionalReaction; rh:25426 rh:substrates/rh:products/rh:equation`
Guanosine-inosine kinase `UniProtKB:P0AEW6`	part_of	inosine/guanosine kinase `MetaCyc:CPLX0-322`	MetaCyc:CPLX0-322 Source assertion: The native complex contains 2 copies of GSK-MONOMER. This preserves the native assembly membership; it does not make an individual subunit an independent catalyst. Source location `CPLX0-322.xml /ptools-xml/Protein/component[Protein/@frameid="GSK-MONOMER"]/(Protein\|coefficient)` UniProtKB:P0AEW6 Source assertion: The reviewed P0AEW6 entry cross-references MetaCyc:GSK-MONOMER and annotates Homodimer. The assembly statement retains its cited experimental evidence. Source location `uniprot-P0AEW6.json /uniProtKBCrossReferences[database="BioCyc",id="MetaCyc:GSK-MONOMER"]; /comments/8` PMID:32857952 Source assertion: SEC-MALS found Gsk dimers without ppGpp and tetramers with ppGpp. GDP also promoted tetramerization less strongly; the dimer/tetramer distribution depends on ligand and protein concentration. Source location `Results: ppGpp tightly binds to Gsk, inhibits its activity and induces tetramerization; Fig. 1D-E; Methods: SEC-MALS, DLS`
Purine nucleoside phosphorylase DeoD-type `UniProtKB:P0ABP8`	part_of	purine nucleoside phosphorylase `MetaCyc:DEOD-CPLX`	MetaCyc:DEOD-CPLX Source assertion: The native complex contains 6 copies of DEOD-MONOMER. This preserves the native assembly membership; it does not make an individual subunit an independent catalyst. Source location `DEOD-CPLX.xml /ptools-xml/Protein/component[Protein/@frameid="DEOD-MONOMER"]/(Protein\|coefficient)` UniProtKB:P0ABP8 Source assertion: The reviewed P0ABP8 entry cross-references MetaCyc:DEOD-MONOMER and annotates Homohexamer; trimer of homodimers. The assembly statement retains its cited experimental evidence. Source location `uniprot-P0ABP8.json /uniProtKBCrossReferences[database="BioCyc",id="MetaCyc:DEOD-MONOMER"]; /comments/10` PMID:235429 Source assertion: Purified E. coli and Salmonella enzymes had approximately six equal subunits; crosslinking supported the hexamer. Association experiments suggested that only the hexamer was active. Source location `Europe PMC core batch /resultList/result[id="235429"]/abstractText; abstract only`
Xanthine-guanine phosphoribosyltransferase `UniProtKB:P0A9M5`	part_of	xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	MetaCyc:GPT-CPLX Source assertion: The native complex contains 4 copies of GPT-MONOMER. This preserves the native assembly membership; it does not make an individual subunit an independent catalyst. Source location `GPT-CPLX.xml /ptools-xml/Protein/component[Protein/@frameid="GPT-MONOMER"]/(Protein\|coefficient)` UniProtKB:P0A9M5 Source assertion: The reviewed P0A9M5 entry cross-references MetaCyc:GPT-MONOMER and annotates Homotetramer. The assembly statement retains its cited experimental evidence. Source location `uniprot-P0A9M5.json /uniProtKBCrossReferences[database="BioCyc",id="MetaCyc:GPT-MONOMER"]; /comments/9` PMID:9100006 Source assertion: The E. coli XPRT structure is a tetramer with 152 residues per subunit. The abstract directly reports this assembly and the phosphoribosyltransferase activity. Source location `Europe PMC core batch /resultList/result[id="9100006"]/abstractText; abstract only`
inosine/guanosine kinase `MetaCyc:CPLX0-322`	catalyzes	guanosine + ATP => GMP + ADP + H(+) `RHEA:27711`	MetaCyc:GUANOSINEKIN-ENZRXN Source assertion: GUANOSINEKIN-ENZRXN explicitly assigns enzyme CPLX0-322 to reaction GUANOSINEKIN-RXN. The chemical normalization is independently supported by reviewed UniProt and the Rhea reaction sides. Source location `GUANOSINEKIN-ENZRXN.xml /ptools-xml/Enzymatic-Reaction/(enzyme/Protein\|reaction/Reaction)` UniProtKB:P0AEW6 Source assertion: Reviewed catalytic activity supports guanosine phosphorylation and its forward physiological direction. Source location `uniprot-P0AEW6.json /comments/1/reaction; /comments/1/physiologicalReactions` PMID:32857952 Source assertion: Gsk dimerization was required for kinase activity in the interface-mutant experiment. ppGpp-bound dimers remained more active than tetramers; this edge denotes the native dimer without asserting exclusive or constitutive oligomeric state. Source location `Results: Gsk restructures both N- and C-termini to bind ppGpp, Fig. 2A and S2D-E; ppGpp inhibits Gsk by blocking conformational dynamics and inducing tetramerization, Fig. 3K`
purine nucleoside phosphorylase `MetaCyc:DEOD-CPLX`	catalyzes	guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	MetaCyc:GUANPHOSPHOR-ENZRXN Source assertion: GUANPHOSPHOR-ENZRXN explicitly assigns enzyme DEOD-CPLX to reaction RXN0-5199. The chemical normalization is independently supported by reviewed UniProt and the Rhea reaction sides. Source location `GUANPHOSPHOR-ENZRXN.xml /ptools-xml/Enzymatic-Reaction/(enzyme/Protein\|reaction/Reaction)` UniProtKB:P0ABP8 Source assertion: Reviewed catalytic activity supports reversible guanosine phosphorolysis; the salvage pathway selects guanine-producing flux. Source location `uniprot-P0ABP8.json /comments/5/reaction; /comments/0`
xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	catalyzes	guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	MetaCyc:GUANPRIBOSYLTRAN-ENZRXN Source assertion: GUANPRIBOSYLTRAN-ENZRXN explicitly assigns enzyme GPT-CPLX to reaction GUANPRIBOSYLTRAN-RXN. The chemical normalization is independently supported by reviewed UniProt and the Rhea reaction sides. Source location `GUANPRIBOSYLTRAN-ENZRXN.xml /ptools-xml/Enzymatic-Reaction/(enzyme/Protein\|reaction/Reaction)` UniProtKB:P0A9M5 Source assertion: Reviewed catalytic activity supports guanine phosphoribosyl transfer; the annotated physiological direction is right-to-left relative to the Rhea master. Source location `uniprot-P0A9M5.json /comments/1/reaction; /comments/1/physiologicalReactions` PMID:9100006 Source assertion: The E. coli tetramer transfers the phosphoribosyl group from PRPP to guanine, xanthine or hypoxanthine, producing their mononucleotides; guanine-to-GMP is the reaction selected here. Source location `Europe PMC core batch /resultList/result[id="9100006"]/abstractText; abstract only`
inosine/guanosine kinase `MetaCyc:CPLX0-322`	has_cofactor	magnesium(2+) `CHEBI:18420`	UniProtKB:P0AEW6 Source assertion: Reviewed cofactor annotation assigns Mg2+ with experimental evidence. The additional free-Mg2+ requirement beyond Mg-ATP remains probable, as stated in the source. Source location `uniprot-P0AEW6.json /comments/3/cofactors[cofactorCrossReference/id="CHEBI:18420"]; /comments/3/note`
xanthine-guanine phosphoribosyltransferase `MetaCyc:GPT-CPLX`	has_cofactor	magnesium(2+) `CHEBI:18420`	UniProtKB:P0A9M5 Source assertion: Reviewed cofactor annotation assigns Mg2+ with experimental evidence from the E. coli structure study. Source location `uniprot-P0A9M5.json /comments/4/cofactors[cofactorCrossReference/id="CHEBI:18420"]` PMID:9100006 Source assertion: The E. coli structure contains magnesium at the PRPP-binding site, interacting with Asp89. This supports bound magnesium without assigning an unsupported per-complex occupancy. Source location `Europe PMC core batch /resultList/result[id="9100006"]/abstractText; abstract only`
guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine `RHEA:13234`	provides_input_for	guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate `RHEA:25426`	MetaCyc:PWY-6620 Source assertion: PWY-6620 explicitly places GUANPRIBOSYLTRAN-RXN downstream of RXN0-5199. Native layouts connect the two reactions through guanine, supplying the phosphoribosyltransferase substrate. Source location `PWY-6620.xml /ptools-xml/Pathway/reaction-ordering[Reaction/@frameid="GUANPRIBOSYLTRAN-RXN"]/predecessor-reactions/Reaction[@frameid="RXN0-5199"]; /reaction-layout` RHEA:13234 Source assertion: The selected phosphorylase reaction produces CHEBI:16235 (guanine). Source location `rhea.rdf.gz; rh:13234 rh:products rh:13233_R; rh:13233_R rh:contains rh:Participant_13233_compound_2523; rh:Compound_2523 rh:chebi` RHEA:25426 Source assertion: The selected phosphoribosyltransferase reaction consumes CHEBI:16235 (guanine). This explicit shared intermediate supports material transfer between these reactions. Source location `rhea.rdf.gz; rh:25426 rh:substrates rh:25424_R; rh:25424_R rh:contains rh:Participant_25424_compound_2523; rh:Compound_2523 rh:chebi`
guanosine 3',5'-bis(diphosphate)(5-) `CHEBI:77828`	inhibits	Guanosine-inosine kinase `UniProtKB:P0AEW6`	PMID:32857952 Source assertion: Purified Gsk bound ppGpp and both guanosine- and inosine-kinase activities were inhibited in vitro. ppGpp blocks conformational dynamics and promotes a less-active tetramer; MG1655-derived mutant studies support physiological regulation. Source location `Results: ppGpp tightly binds to Gsk, inhibits its activity and induces tetramerization, Fig. 1B-C and S1A; Methods: Construction of gsk(WT), ML3271 and gsk(K383A), ML3272`
GDP(3-) `CHEBI:58189`	inhibits The two inspected sources disagree about GTP inhibition. This graph asserts the supported GDP effect and leaves GTP inhibition unresolved; enzyme-level evidence is not a measured rate for every possible substrate.	Guanosine-inosine kinase `UniProtKB:P0AEW6`	PMID:10879466 Source assertion: The purified E. coli guanosine-inosine kinase was markedly inhibited by GDP. The abstract reports maximal activity at an ATP/Mg2+ concentration ratio of 0.5 and also reports GTP inhibition. Source location `Europe PMC core batch /resultList/result[id="10879466"]/abstractText; abstract only` PMID:32857952 Source assertion: GDP bound Gsk and inhibited the inosine-coupled assay less potently than ppGpp; GDP also promoted tetramerization. The Results introduction says GDP, but not GTP or GMP, provides feedback inhibition. Source location `Results: ppGpp tightly binds to Gsk, inhibits its activity and induces tetramerization; Fig. 1B-C,E; Methods: ITC and DLS`

References

MetaCyc:PWY-6579 superpathway of guanine and guanosine salvage (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:PWY-6618 guanine and guanosine salvage III (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:PWY-6620 guanine and guanosine salvage (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:RXN0-5199 RXN0-5199 (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:GUANPRIBOSYLTRAN-RXN GUANPRIBOSYLTRAN-RXN (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:GUANOSINEKIN-RXN GUANOSINEKIN-RXN (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:DEOD-CPLX purine nucleoside phosphorylase (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:GPT-CPLX xanthine-guanine phosphoribosyltransferase (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:CPLX0-322 inosine/guanosine kinase (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:GUANPHOSPHOR-ENZRXN guanosine phosphorylase (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:GUANPRIBOSYLTRAN-ENZRXN guanine phosphoribosyltransferase (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
MetaCyc:GUANOSINEKIN-ENZRXN guanosine kinase (source version: MetaCyc 22.5; original native XML retrieved 2026-10-11)
UniProtKB:P0AEW6 Guanosine-inosine kinase (source version: Reviewed entry version 135, sequence version 1; retrieved 2026-10-11)
UniProtKB:P0ABP8 Purine nucleoside phosphorylase DeoD-type (source version: Reviewed entry version 149, sequence version 2; retrieved 2026-10-11)
UniProtKB:P0A9M5 Xanthine-guanine phosphoribosyltransferase (source version: Reviewed entry version 152, sequence version 1; retrieved 2026-10-11)
PMID:10879466 End-product regulation and kinetic mechanism of guanosine-inosine kinase from Escherichia coli. (source version: Primary abstract inspected in Europe PMC core batch; digest covers full original batch JSON, not article full text)
PMID:9100006 Crystal structure of Escherichia coli xanthine phosphoribosyltransferase. (source version: Primary abstract inspected in Europe PMC core batch; digest covers full original batch JSON, not article full text)
PMID:235429 Purine nucleoside phosphorylase from Escherichia coli and Salmonella typhimurium. Purification and some properties. (source version: Primary abstract inspected in Europe PMC core batch; digest covers full original batch JSON, not article full text)
PMID:32857952 ppGpp Coordinates Nucleotide and Amino-Acid Synthesis in E. coli During Starvation. (source version: Complete primary article HTML inspected; published 2020, PMC availability 2021; retrieved 2026-10-11)
RHEA:27711 guanosine + ATP => GMP + ADP + H(+) (source version: Rhea release 142; digest covers original complete RDF gzip)
RHEA:13234 guanosine + phosphate => alpha-D-ribose 1-phosphate + guanine (source version: Rhea release 142; digest covers original complete RDF gzip)
RHEA:25426 guanine + 5-phospho-alpha-D-ribose 1-diphosphate => GMP + diphosphate (source version: Rhea release 142; digest covers original complete RDF gzip)

Curation history

2026-10-11T03:53:25Z Codex
- CREATE — Add both branches of guanine and guanosine salvage.
  Retained the complete three-reaction native superpathway, condition-dependent Gsk assemblies and supported regulation; preserved conflicting GTP inhibition and historical Gpt assembly evidence. Source dossiers and verification receipts are in research/pathway_additions/2026-10-11-next-186; independent scientific assessments are saved separately.
Read this curation session