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. |
| 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 | MARK AS OVER ANNOTATED | Summary: This broad parent is true but adds no information beyond guanine deaminase activity. Reason: Retain the leaf-level GO:0008892 annotation rather than this generic catalytic class. |
| GO:0016810 hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: This parent class is entailed by the exact guanine deaminase reaction. Reason: GO:0008892 provides the informative substrate-specific molecular function. |
| GO:0019239 deaminase activity | IEA GO_REF:0000118 | MARK AS OVER ANNOTATED | Summary: The broad deaminase term is redundant with guanine deaminase activity. Reason: GO:0008892 captures the same chemistry with the relevant substrate specificity. |
| GO:0046098 guanine metabolic process | IEA GO_REF:0000118 | MARK AS OVER ANNOTATED | Summary: GuaD participates specifically in guanine catabolism rather than an unspecified guanine process. Reason: GO:0006147 is the more informative process term for the direction of this reaction. |
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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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