Alpha-ketoglutarate-dependent xanthine dioxygenase is a non-heme mononuclear Fe(2+) enzyme that decarboxylates alpha-ketoglutarate to succinate and CO(2) while hydroxylating xanthine to generate uric acid (PubMed:15948966). Allows xanthine utilization as a nitrogen source (PubMed:15948966). 2-oxoglutarate + O2 + xanthine = CO2 + succinate + urate Binds 1 Fe(2+) ion per subunit. Leads to cells defective for the utilization of hypoxanthine or xanthine as nitrogen sources, while being still able to utilize uric acid or allantoic acid. Belongs to the TfdA dioxygenase family.