One of the earliest studies reporting the presence of xanthine oxidase in rat skin was made by Barry et al. (1). Westerfeld and Richer-t (2), in a study of the distribution of this enzyme in the tissues of the white rat, confirmed this finding and reported that activity in the skin accounted for approximately 20% of the total xanthine oxidase of the rat. These authors did not study the enzyme i...

I . The oral administration of sodium molybdate caused a rapid rise of molybdenum in the milk of cows and goats fed on a low-molybdenum diet, but did not affect the xanthine oxidase activities of the milk of either species. 2. In the milks of cows not dosed with sodium molybdate, the regression of the xanthine oxidase activity ( y ) on the molybdenum content (x) was found to be (r = +0.9386; P ...

The 6-oxopurine xanthine (Xan, neutral form 2,6-diketopurine) differs from the corresponding 6-oxopurines guanine (Gua) and hypoxanthine (Hyp) in that, at physiological pH, it consists of a approximately 1:1 equilibrium mixture of the neutral and monoanionic forms, the latter due to ionization of N(3)-H, in striking contrast to dissociation of the N(1)-H in both Gua and Hyp at higher pH. In xan...

Xanthine oxidase is a key enzyme which can catalyze hypoxanthine and xanthine to uric acid causing hyperuricemia in humans. Xanthine oxidase inhibitory activities of 24 organic extracts of four species belonging to Citrus genus of the family Rutaceae were assayed in vitro. Since the ethyl acetate extract of C. aurantium dried immature fruits showed the highest xanthine oxidase inhibitory activi...

In peroxisomes isolated from pea leaves (Pisum sativum L.) the production of superoxide free radicals (O(2) (-)) by xanthine and NADH was investigated. In peroxisomal membranes, 100 micromolar NADH induced the production of O(2) (-) radicals. In the soluble fractions of peroxisomes, no generation of O(2) (-) radicals was observed by incubation with either NADH or xanthine, although xanthine oxi...

Xanthine dehydrogenase catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid in the final two steps of the purine degradation process. Xanthine oxidase deficiency is an uncommon cause of pediatric urinary stone formation, and classical xanthinuria. A ten-month-old boy presented with a seven-month history of nausea, vomiting, discomfort during urination, gross hematuria a...

Xanthine dehydrogenase is one of the family of enzymes known as molybdenum-containing hydroxylases [I] . These are complex enzymes, containing two [2Fe-2S] clusters, FAD and the pterin molybdenum cofactor [2]. In Drosophrlu nzelutioguster, xanthine dehydrogenase is encoded by the rosy gene, expression of which affects the eye colour of the flies [3]. More than 200 rosy mutant strains are availa...

Previous studies from this laboratory (1) have demonstrated the existence of several different types of “xanthine oxidase” in nature. The enzymes in milk and mammalian tissues appear to be quite similar, but can be differentiated by the inhibitor Antabuse, which affects only the tissue enzyme (2). Antabuse can also be used to separate the dehydrogenase and oxidase activities of tissue xanthine ...

The xanthine oxidase activity of mouse regenerating liver has been shown to be elevated during the period of rapid liver growth and proliferation. This increase is evident when the enzyme activity is expressed per unit wet tissue weight, per unit nitrogen, or per cell. The adrenal cortex probably plays only a minor role in implementing this phenomenon. Further augmentation of the xanthine oxida...

An optimum way of immobilizing xanthine oxidase on graphite was found where a redox transformation of the enzyme was observed. The nature of the redox maxima was hypothesized on the basis of the dependence of the half-wave potential (Ep/2) on the pH of the solution. The enzymatic activity of xanthine oxidase adsorbed on two kinds of soot was studied by the oxidation of xanthine. The kinetic and...