GuaD is the predicted zinc-dependent guanine deaminase that hydrolytically converts guanine to xanthine and ammonium, supplying xanthine to downstream purine-base oxidation. The exact KT2440 protein has not been characterized biochemically; its assignment is supported by the diagnostic guanine-deaminase family classification, conserved reaction annotation, and PANTHER phylogenetic propagation from characterized orthologs.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005829 cytosol | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: TreeGrafter predicts a soluble cytosolic location for GuaD. Reason: A cytosolic location is compatible with purine-base metabolism, but it is an inferred family-level localization and does not define the enzyme's core function. The TreeGrafter row rests on the PTHR11271 PAINT cytosol node, and Q88F18 is a soluble protein with no predicted signal peptide or transmembrane segment, so the inherited location is plausible. Supporting Evidence: file:interpro/panther/PTHR11271/PTHR11271-paint.tsv PTHR11271 PTN000138454 GO:0005829 C IBD false file:PSEPK/guaD/guaD-uniprot.txt FUNCTION: Catalyzes the hydrolytic deamination of guanine, producing xanthine and ammonia. |
| GO:0006147 guanine catabolic process | IEA GO_REF:0000120 | ACCEPT | Summary: GuaD consumes guanine in the single deamination step that produces xanthine. Reason: This is the immediate biological process of the predicted guanine deaminase reaction. Supporting Evidence: file:PSEPK/guaD/guaD-uniprot.txt PATHWAY: Purine metabolism; guanine degradation; xanthine from guanine: file:interpro/panther/PTHR11271/PTHR11271-paint.tsv PTHR11271 PTN000138455 GO:0006147 |
| GO:0008270 zinc ion binding | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: The guanine-deaminase family is predicted to use one catalytic zinc ion per subunit. Reason: Zinc binding is a credible catalytic cofactor property but is ancillary to the exact guanine deaminase activity. GOA names PTN002259155 in WITH/FROM; the cached family PAINT slice independently records the same term at the experimentally seeded IBD node PTN000138455. Supporting Evidence: file:PSEPK/guaD/guaD-uniprot.txt Note=Binds 1 zinc ion per subunit. file:interpro/panther/PTHR11271/PTHR11271-paint.tsv PTHR11271 PTN000138455 GO:0008270 |
| GO:0008892 guanine deaminase activity | IEA GO_REF:0000120 | ACCEPT | Summary: GuaD is predicted to catalyze guanine hydrolysis to xanthine and ammonium. Reason: The exact reaction, diagnostic InterPro family, and PANTHER node propagated from experimentally annotated orthologs converge on guanine deaminase activity. GOA names PTN002259155 in WITH/FROM, while the cached family PAINT slice independently records the term at IBD node PTN000138455. No direct enzymology has been reported for Q88F18 itself. Supporting Evidence: file:PSEPK/guaD/guaD-uniprot.txt Reaction=guanine + H2O + H(+) = xanthine + NH4(+); file:interpro/panther/PTHR11271/PTHR11271-paint.tsv PTHR11271 PTN000138455 GO:0008892 file:PSEPK/guaD/guaD-deep-research-openscientist.md The gene **guaD** (ordered locus **PP_4281**; UniProt **Q88F18**) of *Pseudomonas putida* strain KT2440 encodes **guanine deaminase** (guanase; EC 3.5.4.3) |
| GO:0016787 hydrolase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: This broad parent is true but adds no information beyond guanine deaminase activity. Reason: GO:0008892 guanine deaminase activity is_a GO:0016787 hydrolase activity, and the specific child is accepted on another row of this review, so the generic catalytic class is true but uninformative. Supporting Evidence: file:PSEPK/guaD/guaD-uniprot.txt Reaction=guanine + H2O + H(+) = xanthine + NH4(+); |
| GO:0016810 hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds | IEA GO_REF:0000002 | TOO GENERAL | Summary: This parent class is entailed by the exact guanine deaminase reaction. Reason: GO:0008892 guanine deaminase activity is_a this carbon-nitrogen hydrolase class, and the specific child is accepted on another row of this review, so the term is true but uninformative. Supporting Evidence: file:PSEPK/guaD/guaD-uniprot.txt Reaction=guanine + H2O + H(+) = xanthine + NH4(+); |
| GO:0019239 deaminase activity | IEA GO_REF:0000118 | TOO GENERAL | Summary: True is_a ancestor of guanine deaminase activity. Reason: GO:0008892 guanine deaminase activity is_a GO:0019239 in the current ontology, so the broad term correctly describes the hydrolytic deamination (guanine + H2O = xanthine + NH4+, EC 3.5.4.3) assigned to Q88F18's guanine-deaminase family. The claim is true, not an over-annotation; it is uninformative because the accepted child term on another row of this review entails it. Supporting Evidence: file:interpro/panther/PTHR11271/PTHR11271-paint.tsv PTHR11271 PTN000138454 GO:0019239 F IBD false file:PSEPK/guaD/guaD-uniprot.txt Reaction=guanine + H2O + H(+) = xanthine + NH4(+); |
| GO:0046098 guanine metabolic process | IEA GO_REF:0000118 | TOO GENERAL | Summary: True is_a ancestor of guanine catabolic process. Reason: GO:0006147 guanine catabolic process is_a GO:0046098 guanine metabolic process, so the propagated parent is true of GuaD's reaction. It is not an over-annotation; it is uninformative because the accepted child term on the UniRule row of this review entails it. Supporting Evidence: file:interpro/panther/PTHR11271/PTHR11271-paint.tsv PTHR11271 PTN000138455 GO:0006147 P IBD false file:PSEPK/guaD/guaD-uniprot.txt PATHWAY: Purine metabolism; guanine degradation; xanthine from guanine: |
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Download this section (compressed HTML)Q: Does purified Q88F18 preferentially deaminate guanine under physiologically relevant conditions in KT2440?
Suggested experts: bacterial purine-catabolism experts
Experiment: Purify Q88F18 and measure zinc-dependent steady-state kinetics for guanine, including a limited alternative-substrate panel to distinguish its primary reaction from possible promiscuous activities.
Type: enzyme activity assay
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