The Activity of the molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase were determined in ammonium sulfate fractions prepared from sheep liver, kidney, lung, small intestines, spleen and heart. In all examined tissues, aldehyde oxidase levels were higher than those of xanthine oxidase; the activity of the former enzyme was the highest in the liver, also present in the lung. Xanthine oxidase activity was not detected in all tissues except the liver. No aldehyde oxidase or xanthine oxidase activity was detected in the small intestine, spleen or
Assiut Vet. Med. J. Vol. 51 No. 104 January 2005
heart. Both Km and Vmax values were determined for phthalazine, 3 methylisoquinoline, phenanthridine and xanthine with hepatic aldehyde oxidase and xanthine oxidase. By using three substrates [phthalazine, 3 methylisoquinoline, phenanthridine] for aldehyde oxidase. Menadione was found to be a competitive inhibitor of this enzyme and the inhibitor constants were calculated.