EC Explorer
[browse EC tree] - [search]
EC 1.17.3.2 Details
show Brenda entryEC number
1.17.3.2
Accepted name
xanthine oxidase
Reaction
xanthine + H2O + O2 = urate + H2O2
Other name(s)
hypoxanthine oxidase,
hypoxanthine:oxygen oxidoreductase,
Schardinger enzyme,
xanthine oxidoreductase,
hypoxanthine-xanthine oxidase,
xanthine:O2 oxidoreductase,
xanthine:xanthine oxidase
Systematic name
xanthine:oxygen oxidoreductase
CAS registry number
9002-17-9
Comment
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].
History
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
back to topEC Tree
1 Oxidoreductases
1.1 Acting on the CH-OH group of donors
1.6.2.1 created 1961, deleted 1965 1.6.2.3 created 1972, deleted 1965
