Xanthine oxidase is a key enzyme responsible for hyperuricemia, a pre-disposing factor for Gout and oxidative stress-related diseases. Only two clinically approved xanthine oxidase inhibitors Allopurinol and Febuxostat are currently used for treatment of hyperuricemia. However, owing to their side effects there is a need for new non-purine-based selective inhibitors of xanthine oxidase. In the ...

Some studies on the effects of xanthine oxidase inhibitor allopurinol [4-hydroxypyrazolo(3,4-d)pyrimidine] on allantoin metabolism of soybean plants (Glycine max cv. Tamanishiki) are reported. Soybean seedlings, aseptically germinated for 96 hours on agar containing 1 millimolar allopurinol, contained only slight amounts of allantoin, allantoic acid, and urea as compared with controls. Analysis...

Chicken liver xanthine dehydrogenase can be partially reduced by either xanthine or NADH. Reduction to approximately the 2-electron-reduced level occurs with NADH, and reduction beyond the 2-electron level occurs with xanthine. In both cases, the reaction is triphasic. The first and third phases are dependent on reductant concentration, whereas the second phase is not. Oxidation of fully (6-ele...

Xanthine oxidoreductase (XOR) is progressively inactivated while catalysing the reduction of inorganic nitrite to NO by xanthine. Inactivation results from conversion of the enzyme into its desulpho-form. The rate of inactivation increases with nitrite concentration. Similar behaviour was shown when NADH replaced xanthine as reducing substrate. A kinetic model is proposed incorporating a 'suici...

To assay the in vitro xanthine oxidase and Tyrosinase inhibitory activity of the alkaloid fractions of the leaves of Indigofera spalathoides and to determine its enzyme inhibition mechanism. Xanthine oxidase and Tyrosinase inhibitory activity was assayed spectrophotometrically under aerobic conditions and the degree of enzyme inhibition was determined by measuring the increase in absorbance at ...

A patient with complete deficiency of xanthine oxidase would not be expected to oxidase allopurinol to oxipurinol if allopurinol did not have any alternative metabolic pathway. 400 mg of allopurinol was administered to a patient with xanthine oxidase deficiency, and plasma allopurinol, oxipurinol, hypoxanthine, and xanthine levels were determined serially by the use of high-performance liquid c...

The quinimine form of p-aminophenol inhibits the oxygen uptake of tissue suspensions and in very small concentrations inhibits specifically the oxidation of hypoxanthine and xanthine to uric acid by the xanthine oxidase of liver (1). Closely related compounds such as o-aminophenol, p-phenylenediamine, and quinone, although they inhibit to different degrees the oxygen uptake of tissues, have no ...

The results of the screening of thirty-one species belonging to the lichen family Graphidaceae for their ability to scavenge superoxide and inhibition of tyrosinase and xanthine oxidase activities have been presented. Graphina glaucorufa, Graphina multistriata, Graphina salacinilabiata, Graphis assamensis, Graphis nakanishiana and Phaeographopsis indica showed strong inhibition of tyrosinase an...

Inhibition of xanthine oxidase by folic acid was reexamined after complete removal of the contaminant which was responsible for time-dependent inactivation (Lewis, A. S., Murphy, L., Mcalla, C., Fleary, M., and Purcell, S. (1984) J. Biol. Chem. 259, 12-15; Spector, T., and Ferone, R. (1984) J. Biol. Chem. 259, 10784-10786). From turnover experiments using stopped flow equipment with a limited a...

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 ...