XdhB encodes the large catalytic subunit of xanthine dehydrogenase, a molybdo-flavoenzyme that catalyzes the two-step oxidation of hypoxanthine to xanthine and xanthine to uric acid during purine catabolism. The protein harbors a molybdopterin cofactor and iron-sulfur cluster essential for substrate oxidation and electron transfer. In Acetobacter pasteurianus, XdhB is crucial for utilizing purines as nitrogen sources and contributes significantly to thermotolerance, with mutations in this gene resulting in thermosensitive phenotypes.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004854 xanthine dehydrogenase activity | IEA GO_REF:0000003 | ACCEPT | Summary: Core catalytic activity of XdhB, well-supported by biochemical characterization in related bacteria and enzyme commission mapping. The protein catalyzes xanthine + NAD+ + H2O → urate + NADH + H+. |
| GO:0005506 iron ion binding | IEA GO_REF:0000002 | ACCEPT | Summary: XdhB contains [2Fe-2S] iron-sulfur clusters essential for electron transfer from the Mo center to FAD/NAD+. This annotation is accurate based on conserved domain analysis. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000120 | REMOVE | Summary: Correct but overly general parent term. The more specific term GO:0004854 (xanthine dehydrogenase activity) is already annotated. |
| GO:0030151 molybdenum ion binding | IEA GO_REF:0000002 | ACCEPT | Summary: XdhB harbors the molybdopterin cofactor essential for catalysis. The Mo center is required for substrate oxidation at the active site. |
| GO:0046872 metal ion binding | IEA GO_REF:0000043 | REMOVE | Summary: Overly general parent term. More specific annotations for iron and molybdenum binding are already present. |
| GO:0051536 iron-sulfur cluster binding | IEA GO_REF:0000043 | ACCEPT | Summary: Correct - XdhB contains [2Fe-2S] clusters for electron transfer. This is more informative than the general iron ion binding term. |
| GO:0051537 2 iron, 2 sulfur cluster binding | IEA GO_REF:0000043 | ACCEPT | Summary: Specific and accurate - UniProt cofactor annotation confirms [2Fe-2S] cluster binding in XdhB. |
| GO:0005737 cytoplasm | IEA | NEW | Summary: XdhB functions in the cytoplasm where it catalyzes purine catabolism as part of the xanthine dehydrogenase complex. Reason: This cellular component term reflects XdhB's cytoplasmic localization where it performs xanthine and hypoxanthine oxidation. Supporting Evidence: file:ACEPA/xdhB/xdhB-deep-research.md XDH catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid in the cytoplasm using NAD+ as electron acceptor |
| GO:0009115 xanthine catabolic process | IEA | NEW | Summary: XdhB catalyzes the oxidation of xanthine to uric acid as part of purine catabolism using NAD+ as electron acceptor. Reason: This biological process term captures XdhB's central role in xanthine catabolism through the xanthine dehydrogenase pathway. Supporting Evidence: file:ACEPA/xdhB/xdhB-deep-research.md XDH catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid in the cytoplasm using NAD+ as electron acceptor |
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)