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Xanthine Oxidase
Xanthine oxidase (XO, sometimes XAO) is a form of xanthine oxidoreductase, a type of enzyme that generates reactive oxygen species. These enzymes catalyze the oxidation of hypoxanthine to xanthine and can further catalyze the oxidation of xanthine to uric acid. These enzymes play an important role in the catabolism of purines in some species, including humans. Xanthine oxidase is defined as an ''enzyme activity'' (EC 1.17.3.2). The same protein, which in humans has the HGNC approved gene symbol ''XDH'', can also have xanthine dehydrogenase activity (EC 1.17.1.4). Most of the protein in the liver exists in a form with xanthine dehydrogenase activity, but it can be converted to xanthine oxidase by reversible sulfhydryl oxidation or by irreversible proteolytic modification. Reaction The following chemical reactions are catalyzed by xanthine oxidase: * hypoxanthine + H2O + O2 \rightleftharpoons xanthine + H2O2 * xanthine + H2O + O2 \rightleftharpoons uric acid + H2O2 * Xant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xanthine Dehydrogenase
Xanthine dehydrogenase, also known as XDH, is a protein that, in humans, is encoded by the ''XDH'' gene. Function Xanthine dehydrogenase belongs to the group of molybdenum-containing hydroxylases involved in the oxidative metabolism of purines. The enzyme is a homodimer. Xanthine dehydrogenase can be converted to xanthine oxidase by reversible sulfhydryl oxidation or by irreversible proteolytic modification. Xanthine dehydrogenase catalysis, catalyzes the following chemical reaction: xanthine + NAD+ + H2O \rightleftharpoons urate + NADH + H+ The three substrate (biochemistry), substrates of this enzyme are xanthine, nicotinamide adenine dinucleotide, NAD+, and water, H2O, whereas its three product (chemistry), products are urate, nicotinamide adenine dinucleotide, NADH, and hydrogen ion, H+. This enzyme participates in purine metabolism. Nomenclature This enzyme belongs to the family of oxidoreductases, to be specific, those acting on CH or CH2 groups with NAD+ or NAD ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
