The reductive metabolism of 2-nitrofluorene, a carcinogenic air pollutant, in rat skin microsomes and cytosol was investigated. 2-Nitrofluorene was reduced to the corresponding amine by the microsomes with NADPH and by the cytosol with 2-hydroxypyrimidine or 4-hydroxypyrimidine under anaerobic conditions. The cytosolic activity was much higher than that of skin microsomes. The 2- or 4-hydroxypy...

The acetaldehyde-xanthine oxidase system in the presence and absence of myeloperoxidase (MPO) and chloride has been employed as a model of the oxygen-dependent antimicrobial systems of the PMN. The unsupplemented xanthine oxidase system was bactericidal at relatively high acetaldehyde concentrations. The bactericidal activity was inhibited by superoxide dismutase (SOD), catalase, the hydroxyl r...

BACKGROUND Oxidative stress plays important role in the pathogenesis of atherosclerosis and coronary artery disease (CAD). We aimed to determine the sources and selected molecular mechanisms of oxidative stress in CAD. METHODS AND RESULTS We examined basal and NAD(P)H oxidase-mediated superoxide (O2*-) production using lucigenin chemiluminescence, ferricytochrome c and dihydroethidium fluores...

Passive Heymann nephritis (PHN) in rats is a model of human membranous nephropathy characterized by formation of subepithelial immune deposits in the glomerular capillary wall and complement activation. Oxygen radicals have been implicated in the subsequent glomerular damage which leads to proteinuria. This study examines the involvement of xanthine oxidase in this process. Xanthine oxidase act...

A variety of purine and azapurine analogues have been shown to serve as substrates for and inhibitors of xanthine oxidase. Thus, in addition to its usual substrates, hypoxanthine and xanthine, and its demonstrated activity on certain pterines (I), pyrimidines (2)) and aldehydes (3), the following purine analogues are oxidized by xanthine oxidase: adenine (4), 2-azaadenine (5), 6-mercaptopurine ...

Studies, undertaken in this laboratory to evaluate the effect, of riboflavin antagonists on mammalian flavoenzymes, have necessitated the investigation of the xanthine oxidase activity of mouse tissue. In general, little difficulty has been encountered in the manometric determination of xanthine oxidase (1) in tissues of high enzymatic activity, e.g. liver and small intestine, although irregula...

5-Ethynyluracil is a time-dependent and tight binding inhibitor of xanthine oxidase. The maximal value of the first-order rate constant for onset of inhibition is 0.01 s-1, and the concentration of 5-ethynyluracil which gives one-half of this value is 190 microM. Because the t1/2 for formation of active enzyme from inhibited enzyme is greater than 30 h in the absence of NADH, inhibition of xant...

The reduction of cytochrome c by xanthine oxidase and the competitive inhibition of this process by carbonic anhydrase and by myoglobin have been studied by kinetic and by equilibrium binding methods. Carbonic anhydrases isolated from bovine and from human erythrocytes differed strikingly in their ability to inhibit competitively the reduction of cytochrome c. The KS for cytochrome c was a func...

In 1948 Miller (1) demonstrated that the loss of liver xanthine oxidase activity in the rat greatly exceeded the loss of liver protein during acute inanition. Moreover, xanthine oxidase appeared to be the most labile of the four liver enzymes studied. Westerfeld and Richert (2) observed that increasing the level of protein in the diet tended to bring about an increase in liver xanthine oxidase ...

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...