Oxidoreductases;
Acting on CH or CH2 groups;
With NAD+ or NADP+ as acceptor
BRITE hierarchy

xanthine:NAD+ oxidoreductase

xanthine + NAD+ + H2O = urate + NADH + H+ [RN:R02103]

R02103;
(other) R01768 R12987 R12988
Reaction

xanthine [CPD:C00385];
NAD+ [CPD:C00003];
H2O [CPD:C00001]

Acts on a variety of purines and aldehydes, including hypoxanthine. The mammalian enzyme can also convert all-trans retinol to all-trans-retinoate, while the substrate is bound to a retinoid-binding protein [14]. The enzyme from eukaryotes contains [2Fe-2S], FAD and a molybdenum centre. The mammalian enzyme predominantly exists as the NAD-dependent dehydrogenase (EC 1.17.1.4). During purification the enzyme is largely converted to an O2-dependent form, xanthine oxidase (EC 1.17.3.2). The conversion can be triggered by several mechanisms, including the oxidation of cysteine thiols to form disulfide bonds [2,6,8,15] [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 [2,7,15].

EC 1.17.1.4 created 1972 as EC 1.2.1.37, transferred 1984 to EC 1.1.1.204, modified 1989, transferred 2004 to EC 1.17.1.4, modified 2011