Xenobiotic metabolism xanthine oxidase

A number of other enzymes, such as monoamine oxidase, alcohol dehydrogenase and xanthine oxidase, are also involved in drug metabolism. These enzymes tend to be more specific, oxidizing xenobiotics related to the normal substrate for the enzyme. 

Xanthine oxidase (EC 1.2.3.2) catalyzes the formation of uric acid, an end-product of purine catabolism. The mammalian enzyme is a metalloflavoprotein composed of two subunits containing molybdenum, FAD and Fe/S clusters as prosthetic groups in a ratio of 1 1 4 per subunit (1). Besides its endogenous metabolic function, xanthine oxidase is also active toward a wide spectrum of oxidizable xenobiotic substrates. Although some cestodes and trematodes produce trace amounts of uric acid (16), the presence of xanthine oxidase activity in these organisms has not been demonstrated. Xanthine oxidase was found in the cytosolic fractions of the nematodes Ancylostoma ceylanicum and Nippostrongylus brasiliensis (17), but its activity toward xenobiotic substrates was not tested. 

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