Oxygen free radicals generated by xanthine oxidase have been implicated in cardiac damage. The activity of xanthine oxidase/reductase in adult rat heart is considerable. Its assay gives controversial results for other species, for example, rabbits and humans. Therefore, we perfused isolated hearts of various species, including explanted human hearts, to measure the conversion of exogenous hypox...

In the previous paper (1) milk xanthine oxidase was reported to oxidize quaternary, heterocyclie compounds only at pH values above 9.6, whereas purines and aldehydes are most rapidly oxidized at neutral pH. This specificity change was attributed to an alteration in the substrate-binding site brought about by the titration of a group or groups with a pK, value of about 10.7. This suggestion prom...

We have recently reported that xanthine oxidase is involved in the generation of free radicals in exhaustive exercise. Allopurinol, an inhibitor of xanthine oxidase, prevents it. The aim of the present work was to elucidate the role of exercise-derived reactive oxygen species in the cell signalling pathways involved in the adaptation to exercise in man. We have found that exercise causes an inc...

Hyperuricemia is a purine metabolism disorder characterised by an excess of uric acid in the blood and considered as risk factor for gout, coronary heart disease, hypertension, diabetes, variety other illnesses. Xanthine oxidase inhibitors have key role management hyperuricemia related disorders but multiple adverse effects associated with these agents minimized their chronic use. Ficus carica ...

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...

Previous papers in this series have reported the hypoxanthinedependent oxidation of sulfite by cyanide-inhibited xanthine oxidase (1) and experiments which permitted postulation of the structure of the active site of this enzyme (2). In the present study, xanthine oxidase acting on its substrates has been found to initiate the aerobic oxidation of sulfite by free radical chains of great length ...

A new preparative procedure for bovine milk xanthine oxidase avoids exposure of the enzyme to proteases. The enzyme so obtained exhibited a molecular weight of about 300,000 as did chicken liver xanthine dehydrogenase. The former readily yielded species with a molecular weight of 150,000 in guanidine and in acid but could not be resolved into smaller subunits. Aldehyde oxidase of rabbit liver e...

1. Rate sedimentation and isopycnic centrifugation were used to analyse the subcellular sites of enzymes in homogenates of goldfish intestinal mucosa. 2. The results allowed the following allocations to be made: carnitine acetyl transferase-mitochondrial and peroxisomal, xanthine dehydrogenase and NAD: alpha-glycerophosphate dehydrogenase soluble phase, NADP: isocitrate dehydrogenase soluble ph...

The presence of the xanthine oxidase enzyme system has been demonstrated in the rheumatoid synovium. This supplies a reactive oxygen species generating system to synovium that is subjected to hypoxic-reperfusion cycles (cf inflamed rheumatoid synovium). An antibody to bovine milk xanthine oxidase has been used to localise the enzyme by immunohistochemistry to synovial endothelium. This implicat...

Despite the important role of pyrazinamide in tuberculosis treatment, little is known about the mechanism of pyrazinamide-induced hepatotoxicity. We inhibited xanthine oxidase in HepG2 cells by using a nontoxic concentration of allopurinol, a well-known xanthine-oxidase inhibitor. This increased in vitro pyrazinamide toxicity in HepG2 cells, which suggests that the hydroxy metabolites of pyrazi...