In 1948 Keith et al. (1) demonstrated that in chicks fed a folic aciddeficient diet liver xanthine oxidase activity was far higher than that observed in birds receiving adequate levels of folic acid. It was postulated (2, 3) that 6-formylpteridine, a potent inhibitor of xanthine oxidase in vitro, was biologically active in controlling the oxidation of xanthine and hypoxanthine in vivo, since 6-...

The twin character of reactive oxygen species is substantiated by a growing body of evidence that reactive oxygen species within cells act as inducers and accelerators of the oncogenic phenotype of cancer cells, while reactive oxygen species can also induce cancer cell death and can therefore function as anti-tumorigenic species. The aim of this study was to assess a possible influence of xanth...

In a previous study (1) it was shown that dogs maintained on a purified diet developed a defect in acetaldehyde metabolism. Of the five known enzyme systems that could theoretically be involved in acetaldehyde metabolism in viva (aldolase, mutase, carboxylase, aldehyde ox&se, and xanthine oxidase), the xanthine and aldehyde oxidases seemed most likely to be dependent upon a dietary factor not a...

Various purine analogs active as carcinostatic agents have previously been shown to act as po tent inhibitors of xanthine oxidase in vitro in both homogenate and isolated enzyme systems (4, 5). 8-Azaguanine (8-AG) has been demonstrated to be an in vitro inhibitor of both xanthine oxidase and uricase (4, 9). Elion et al. have reported that 6mercaptopurine (6-MP) is a substrate for xanthine oxida...

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...

Xanthine phosphoribosyltransferase (XPRT) and hypoxanthine-guanine (HGPRT) are purine salvaging enzymes of Leishmania donovani with distinct 6-oxopurine specificities. LdXPRT phosphoribosylates xanthine, hypoxanthine, guanine, preference toward whereas LdHGPRT only hypoxanthine guanine. In our study, was used as a model to understand these base Mutating I209 V, the conserved residue found in HG...

Alcaligenes jaecalis is capable of growing in response to simple pteridines as the sole source of nitrogen (1). Simple pteridines appear to be metabolized in this organism through the common intermediate, tetraoxypteridine (1, 2)) and cell-free extracts of the organism catalyze the conversion of tetraoxypteridine to xanthine-8-carboxylic acid (1). In these conversions the nitrogen atoms of the ...

The systematic study of the substrate specificity of mammalian xanthine oxidase has indicated a common mechanism by which various purines may be dehydrogenated (1). The results obtained also made it clear why methylated xanthines, with the exception of 1-methylxanthine (2), cannot be oxidized by xanthine oxidase to the corresponding substituted uric acids (3, 4). Therefore, another source had t...