| Synonyms |
AXOR, EC 1.1.3.22, EC 1.2.3.2., hypoxanthine oxidase, hypoxanthine-xanthine oxidase, hypoxanthine:oxygen oxidoreductase, More, oxidase, xanthine, Schardinger enzyme, xanthine dehydrogenase/oxidase, xanthine oxidase, xanthine oxidoreductase, xanthine: oxygen oxidoreductase, xanthine:O2 oxidoreductase, xanthine:oxygen oxidoreductase, xanthine:xanthine oxidase, XnOx, XO, XOD, XOR |
| Comments |
An iron-molybdenum flavoprotein (FAD) containing [2Fe-2S] centres. Also oxidizes hypoxanthine, some other purines and pterins, and aldehydes, but is distinct from EC 1.2.3.1, aldehyde oxidase. Under some conditions the product is mainly superoxide rather than peroxide: R-H + H2O + 2 O2 = ROH + 2 O2?- + 2 H+. The mammallian enzyme predominantly exists as an NAD-dependent dehydrogenase (EC 1.17.1.4, xanthine dehydrogenase). During purification the enzyme is largely converted to the O2-dependent xanthine oxidase form (EC 1.17.3.2). The conversion can be triggered by several mechanisms, including the oxidation of cysteine thiols to form disulfide bonds [4,5,7,10] [which can be catalysed by EC 1.8.4.7, enzyme-thiol transhydrogenase (glutathione-disulfide) in the presence of glutathione disulfide] or limited proteolysis, which results in irreversible conversion. The conversion can also occur in vivo [4,6,10]. |
