Amplite? Colorimetric Xanthine Oxidase Assay Kit. Xanthine oxidase (XO)is an enzyme that catalyzes the oxidation of hypoxanthine to xanthine and can further catalyze the oxidation of xanthine to uric acid. It plays an important role in the catabolism of purines. Xanthine oxidase is normally found in liver and jejunum. During severe liver damage, xanthine oxidase is released into blood, so a blood assay for XO is a way to determine if liver damage has happened. Xanthinuria is a rare genetic disorder where the lack of xanthine oxidase leads to high concentration of xanthine in blood and can cause health problems such as renal failure. The Amplite? Colorimetric Xanthine Oxidase Assay Kit provides a quick and ultrasensitive method for the measurement of xanthine oxidase activities. It can be performed in a convenient 96-well or 384-well microtiter-plate format and easily adapted to automation without a separation step. In the assay, xanthine oxidase catalyzes the oxidation of purine bases, hypoxanthine or xanthine to uric acid and superoxide , which spontaneously degrades to hydrogen peroxide (H2O2). The kit uses our Amplite? Red substrate which enables a dual recordable mode. The color signal can be easily read at ~570 nm with an absorbance microplate reader. With the Amplite? Colorimetric Xanthine Oxidase Assay Kit, we have detected as little as 0.3 mU/mL xanthine oxidase in a 100 μL reaction volume.