Xanthine Oxidase (XO) belongs to the class of complex metalloflavoproteins. It is produced by oxidation of sulfhydryl residues or by proteolysis of xanthine dehydrogenase (XDH). XO and XDH plays a vital role in the last two steps in the formation of urate. Elevated levels of XO has been observed in the serum of chronic liver disease patients. Therefore, XO can be used as a biomarker for the detection of liver disease.
Xanthine oxidase activity is inhibited by folic acid.
Xanthine oxidase is a molybdenum-containing enzyme that is found in the cytosol, and may be strongly inhibited by flavonoids. It plays a vital role in the metabolism of some drugs, as well as purines and pyrimidines. It is also known to be a biological source of reactive oxygen species.
Suspension in 2.3 M (NH4)2SO4, 10 mM sodium phosphate buffer, pH 7.8, containing 1 mM EDTA and 1 mM sodium salicylate