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ENZYME entry: EC

Accepted Name
xanthine oxidase.
Alternative Name(s)
hypoxanthine oxidase.
hypoxanthine-xanthine oxidase.
Schardinger enzyme.
xanthine oxidoreductase.
Reaction catalysed
H2O + O2 + xanthine <=> H2O2 + urate
  • Also oxidizes hypoxanthine, some other purines and pterins, and aldehydes, but is distinct from EC
  • 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
  • During purification the enzyme is largely converted to the O2-dependent xanthine oxidase form (EC
  • The conversion can be triggered by several mechanisms, including the oxidation of cysteine thiols to form disulfide bonds (which can be catalyzed by EC in the presence of glutathione disulfide) or limited proteolysis, which results in irreversible conversion.
  • The conversion can also occur in vivo.
  • Formerly EC and EC
PRIAM enzyme-specific profiles1.17.3.2
KEGG Ligand Database for Enzyme Nomenclature1.17.3.2
IUBMB Enzyme Nomenclature1.17.3.2
MEDLINEFind literature relating to
Rhea expert-curated reactions1.17.3.2
P80457, XDH_BOVIN;  P47990, XDH_CHICK;  Q9MYW6, XDH_FELCA;  
P47989, XDH_HUMAN;  Q00519, XDH_MOUSE;  P22985, XDH_RAT;  

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