Description_x000D_ General description_x000D_ Formerly E.C. 1.1.3.22_x000D_ Application_x000D_ Xanthine Oxidase from bovine milk has been used:_x000D_ • as a source for superoxide generation_x000D_ • for the degradation of hypoxanthine_x000D_ • for the detection of reactive oxygen species (ROS) in lipid model by electron spin resonance (ESR) spin trap method_x000D_ • as a constituent of assay mixture in xanthine oxidase inhibition assay_x000D_ Biochem/physiol Actions_x000D_ 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._x000D_ Xanthine oxidase activity is inhibited by folic acid._x000D_ 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._x000D_ Unit Definition_x000D_ One unit will convert 1.0 μmole of xanthine to uric acid per min at pH 7.5 at 25 °C. Approx. 50% of the activity is obtained with hypoxanthine as substrate._x000D_ Physical form_x000D_ Suspension in 2.3 M (NH4)2SO4, 10 mM sodium phosphate buffer, pH 7.8, containing 1 mM EDTA and 1 mM sodium salicylate_x000D_ Preparation Note_x000D_ Chromatographically purified_x000D_ Analysis Note_x000D_ Protein determined by biuret