A new group of compounds analogous to the purines was recently described (1) in which carbon atom 2 of the purine ring was replaced by nitrogen. One of these imidazo-1 ,2,3-triazines (I), conveniently called 2-azaadenine, was shown to be an antagonist of hypoxanthine and of adenine in its toxic action against bacteria and mice. The corresponding hydroxy compound, 2-azahypoxanthine, was relative...

The oxidation of hypoxanthine to xanthine and of xanthine to uric acid is catalysed by xanthine oxidase (EC 1.2.3.2). This enzyme has been considered to be an oxidase in mammalian organs (De Renzo, 1956), whereas it is a dehydrogenase in the organs of birds, with NAD+ probably being the physiological electron acceptor (Morell, 1955a,b; Fellig & Wiley, 1958). We have reported that in freshly pre...

Molybdenum hydroxylases, aldehyde oxidase and xanthine oxidoreductase, were shown to be involved in the nitroreduction of 2-nitrofluorene (NF), 1-nitropyrene, and 4-nitrobiphenyl, environmental pollutants, in the skin of various mammalian species. NF was reduced to 2-aminofluorene by hamster skin cytosol in the presence of 2-hydroxypyrimidine, 4-hydroxypyrimidine, N(1)-methylnicotinamide, or be...

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...