41. Models for hemerythrin, an enzyme with a diiron active site, and xanthine oxidase, a molybdoenzyme, have been examined. 42. Allopurinol is a drug that inhibits the enzyme xanthine oxidoreductase and, thus, lowers the level of uric acid in the body. 43. In a 24-hour urine excretion of more than 800 mg, which indicates overproduction, a xanthine oxidase inhibitor is preferred. 44. Hypoxanthine is then oxidatively catabolized first to xanthine and then to uric acid, and the reaction is catalyzed by the enzyme xanthine oxidase: 45. Hypoxanthine is then oxidatively catabolized first to xanthine and then to uric acid, and the reaction is catalyzed by the enzyme xanthine oxidase: 46. A 24-hour urine excretion of more than 800 mg, which indicates overproduction, is an indication for a xanthine oxidase inhibitor. 47. Because xanthine oxidase is a metabolic pathway for uric acid formation, the xanthine oxidase inhibitor allopurinol is used in the treatment of gout. 48. Because xanthine oxidase is a metabolic pathway for uric acid formation, the xanthine oxidase inhibitor allopurinol is used in the treatment of gout. 49. They contain caffeine ( known in some parts of the world as mateine ) and also contains related xanthine alkaloids and are harvested commercially. 50. Xanthine oxidase also produces uric acid, which may act as both a prooxidant and as a scavenger of reactive species such as peroxynitrite.
