Xanthine Oxidase (bovine)

Xanthine oxidase (XO) is a complex metalloflavoprotein involved in purine catabolism, oxidative stress, and xenobiotic metabolism, among other processes. It exists as a homodimer and each monomer is composed of an N-terminal domain that contains two unequal iron-sulfur clusters, an intermediate domain that contains the FAD cofactor, and a C-terminal domain that contains the molybdopterin cofactor. XO is primarily expressed in the liver and intestines, has been found in blood, serum, and milk, and localizes to the cytosol, cell membrane, and peroxisomes.1 It is produced by irreversible or reversible post-translational modification of xanthine dehydrogenase (XD) via limited proteolysis or oxidation of XD thiol groups, respectively. XO catalyzes the conversion of hypoxanthine to xanthine to uric acid and uses molecular oxygen as the electron acceptor, compared with XD that uses NAD+, and this results in the generation of hydrogen peroxide and superoxide, which can react with nitric oxide (NO) to produce peroxynitrite. In hypoxic conditions, XO converts nitrates and nitrite to NO. Increased blood levels of XO's enzymatic product uric acid, hyperuricemia, is associated with several diseases, including gout, cardiovascular disease, ischemia-reperfusion injury, obesity, and diabetes. XO has commonly been used in coupled enzyme assays to measure superoxide dismutase (SOD) activity. Cayman's Xanthine Oxidase (bovine) protein can be used for enzyme activity assays. Protein function: Key enzyme in purine degradation. Catalyzes the oxidation of hypoxanthine to xanthine. Catalyzes the oxidation of xanthine to uric acid. Contributes to the generation of reactive oxygen species. [The UniProt Consortium]