Xanthine Oxidase (XO) 學生 : 李威聰 指導老師 : 李惠春
Introduction Function Structure Property Gout
Function In purine degradation, it oxidizes hypoxanthine successively to xanthine and then to uric acid
Stucture Homodimer Each monomer has three domains N-terminal domain (residues 1~165): N-terminal domain (residues 1~165): two Fe/S cofactors two Fe/S cofactors FAD-binding domain (residues FAD-binding domain (residues 226~553) 226~553) The third domain (residues The third domain (residues 590~1332): one molybdenum 590~1332): one molybdenum
Fe/S convert XDH (xanthine dehydrogenase) to XO dehydrogenase) to XO FAD reduction of O 2 FAD reduction of O 2 Molybdenum oxidative hydroxylation Molybdenum oxidative hydroxylation of purine of purine
Property Ubiquitous among species and within the various tissues Normally it exists in the liver and jejunum determination of serum xanthine determination of serum xanthine oxidase level serves as a sensitive oxidase level serves as a sensitive indicator of acute liver damage indicator of acute liver damage
In individuals, 90% is XDH form, and 10% is XO form 10% is XO form XDH XO (oxidation of sulfhydryl or XDH XO (oxidation of sulfhydryl or proteolysis) proteolysis) Difference between XO & XDH: XO XH+H 2 O+O 2 X=O+H 2 O 2 XO XH+H 2 O+O 2 X=O+H 2 O 2 XDH XH+H 2 O+NAD + X=O+NADH XDH XH+H 2 O+NAD + X=O+NADH
Other names: xanthine oxidoreductase, hypoxanthine oxidase, hypoxanthine- xanthine oxidase
Gout A form of arthritis caused by excess uric acid (hyperuricemia) Complication can result death Cause: heredity, diet, fatness, sex, excessive exercise, drug, alcohol, and some diseases
Drug can decrease patients’ pains and prevent it an attack of acute gout: colchicine an attack of acute gout: colchicine lower conc. of uric acid: allopurinol lower conc. of uric acid: allopurinol