Oxidoreductases;
Acting on CH or CH2 groups;
With oxygen as acceptor
BRITE hierarchy

xanthine:oxygen oxidoreductase

xanthine + H2O + O2 = urate + H2O2 [RN:R02107]

R02107;
(other) R00069 R01769 R07942 R07977 R07978 R07979 R08235 R12989 R12990
Reaction

xanthine [CPD:C00385];
H2O [CPD:C00001];
O2 [CPD:C00007]

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: RH + H2O + 2 O2 = ROH + 2 O2.- + 2 H+. The mammalian 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].

EC 1.17.3.2 created 1961 as EC 1.2.3.2, transferred 1984 to EC 1.1.3.22, modified 1989, transferred 2004 to EC 1.17.3.2, modified 2011