Superoxide dismutase exerted a pronounced inhibitory effect upon xanthine oxidase-mediated reduction of iron in ferritin, ferric chloride, or ferric ADP. Maximal inhibition was observed when the superoxide dismutase concentration was only about 1% of that found in normal porcine liver. These observations indicate that superoxide anion radical is an intermediate in the reduction of iron by xanth...

Chemistry and Biochemistry of Flavoenzymes (Muller, F., ed.), vol. 111, pp. 309-317, CRC Press, Boca Raton 7 Ratti, S., Curti, B., Zanetti, G. and Galli, E. (1985) J. Bacteriol. 163, 724-729 8 Vanoni, M. A., Negri, A., Zanetti, G., Ronchi, S. and Curti, B. (1990) Biochem. Biophys. Acta 1039, 374-377 9 Vanoni, M. A., Nuzzi, L., Rescigno, M., Zanetti, G. and Curti, B. (1991) Eur. J. Biochem. 202,...

Nitric oxide provokes vasodilation and inhibits platelet aggregation. We examined the effect of nitric oxide on superoxide anion production by three sources: activated intact neutrophils, xanthine oxidase/hypoxanthine, and the NADPH oxidase. Nitric oxide significantly inhibited the generation of superoxide anion by neutrophils exposed to either FMLP (10(-7)M) or PMA (150 ng/ml) (IC50 = 30 micro...

A number of substances such as oxygen, dyes, and nitrate can act as hydrogen acceptors for xanthine oxidase (1). It has now been found that cytochrome c is also reduced by this system. Since only one other enzyme has been isolated which reduces cytochrome c (2), it was of interest to study the reaction, particularly since Ball (3) has indicated that xanthine oxidase is a flavoprotein. The activ...

This work describes QSAR and SAR studies on the reduction of 27 aromatic nitro compounds by xanthine oxidase using both distance-based topological indices and quantum molecular descriptors along with indicator parameters. The application of a multiple linear regression analysis indicated that a combination of distance-based topological indices with the ad hoc molecular descriptors and the indic...

For many years it has been known that numerous compounds can act as inhibitors of xanthine oxidase in vitro. This has been demonstrated for such diverse substances as cyanide (I), copper (Z), oxidized p-aminophenol (3), pyrogallol (4), 6-pteridylaldehyde (5), Antabuse (6), and numerous flavonoids (7). Few, if any, of the above inhibitors can be considered as being present and normally participa...

BACKGROUND/AIMS The oxidation of xenobiotic-derived aromatic aldehydes with freshly prepared liver slices has not been previously reported. The present investigation compares the relative contribution of aldehyde oxidase, xanthine oxidase and aldehyde dehydrogenase activities in the oxidation of vanillin, isovanillin and protocatechuic aldehyde with freshly prepared liver slices. METHODS Vani...

When investigating the potential for xanthine oxidase (XO)-mediated metabolism of a new chemical entity in vitro, selective chemical inhibition experiments are typically used. Most commonly, these inhibition experiments are performed using the inhibitor allopurinol (AP) and commercially prepared human liver cytosol (HLC) as the enzyme source. For reasons detailed herein, it is also a common pra...

For many years it has been known that numerous compounds can act as inhibitors of xanthine oxidase in vitro. This has been demonstrated for such diverse substances as cyanide (I), copper (Z), oxidized p-aminophenol (3), pyrogallol (4), 6-pteridylaldehyde (5), Antabuse (6), and numerous flavonoids (7). Few, if any, of the above inhibitors can be considered as being present and normally participa...