Xanthine Oxidase Assay

Xanthine Oxidase (XO) located predominantly in the liver and intestine in mammalian tissues and catalyzes the hydroxylation of hypoxanthine to xanthine and then to uric acid and hydrogen peroxide. XO activity is normally very low in blood and liver injury can result in the release of XO into blood. XO activity or expression can be up-regulated in gout and cardiovascular disease. This colorimetric assay is based on XO-catalyzed oxidation of xanthine, in which the formed hydrogen peroxide is catalyzed by peroxidase and reacts with 4-aminoantipyrine to form the product dye. The color intensity of the reaction product at 550nm is directly proportional to XO activity in the sample.