Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.17.3.2 (xanthine oxidase)
8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The absorption of xanthine oxidase into the bloodstream was studied in rabbits given a milk/cream preparation, fortified with 130 U bovine milk xanthine oxidase or the milk/cream preparation alone (control). The preparations were injected trans-abdominally into the intestines. The rise of plasma xanthine oxidase/dehydrogenase activity was studied with a radioenzymatic assay with and without NAD+. In rabbits, which received the fortified mixture, the plasma xanthine oxidase increase in 8 h was six times more than the increase in control animals (P less than 0.001). In both groups plasma xanthine dehydrogenase activity increased 3-4 times (P less than 0.001), without a significant difference between the two groups. We estimate that only 0.003%, or about 3 micrograms, of the xanthine oxidase added, is absorbed as an active enzyme from the intestine.
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PMID:Xanthine oxidase in rabbit plasma after application of a bovine milk preparation to small intestine. 608 54

Carbon monoxide:methylene blue oxidoreductase, the key enzyme of CO-oxidation in energy metabolism of the carboxydobacterium Pseudomonas carboxydovorans, has been isolated in good yield and purity and found to contain FAD, molybdenum, iron, and labile sulfide in the ratio of 1:1:4:4. The enzyme is, therefore, a new molybdenum-containing iron-sulfur flavoprotein, exhibiting chemical and spectral properties quite similar to those of xanthine oxidase. Analytical data on the spectral characteristics of the enzyme in the oxidized and various reduced states are presented. Carbon monoxide:methylene blue oxidoreductase turned out to be photoreducible in the presence of EDTA and urea and was subject to reoxidation by air oxygen; no flavoprotein semiquinone was formed. Unphysiological electron acceptors, e.g. methylene blue, were used as oxidizing substrates whereas NAD or NADP turned out to be ineffective. Methylene blue reduction with CO was not affected by the presence of allopurinol, and carbon monoxide:methylene blue oxidoreductase was not able to catalyze the reduction of methylene blue with xanthine, adenine, or aldehydes. CO was the only reducing substrate used by the enzyme. Carbon monoxide:methylene blue oxidoreductase formed no sulfite adduct, and the reactivity with ferricyanide or cytochrome c was significant but slow. As known for other molybdenum hydroxylases, carbon monoxide:methylene blue oxidoreductase was rapidly inactivated by methanol, but the enzyme exhibited no ability to catalyze the oxidation of NADH with methylene blue, and NAD was not able to overcome methanol inhibition.
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PMID:Chemical and spectral properties of carbon monoxide: methylene blue oxidoreductase. The molybdenum-containing iron-sulfur flavoprotein from Pseudomonas carboxydovorans. 627 81

When heart or liver mitochondria are exposed to superoxide radicals generated from xanthine + xanthine oxidase their ability to take up and to retain Ca2+ is impaired. The rate of oxidation of pyruvate + malate as substrates is diminished and the appearance of thiol groups when the mitochondria are supplied with these substrates is abolished. These inhibitory effects are offset if respiration is supported by succinate in presence of rotenone provided that a substrate (beta-hydroxybutyrate) is provided to maintain the reduction of NADH. The data agree with the thesis that a generation of thiol groups is essential to maintain membrane integrity and that the generation depends on provision of reduced NAD(P)H.
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PMID:The effect of superoxide generation on the ability of mitochondria to take up and retain Ca2+. 629 91

NAD(P)H oxidation is frequently measured to assay the activity of the neutrophil O-2-generating oxidase. It was found that 10(-4) M ethylene glycol bis (beta-aminoethyl ether)-N-N'-tetraacetic acid (EGTA) increased NAD(P)H oxidation by the 27,000 g granule fraction of resting and stimulated human neutrophils without altering net O-2 production. The commonly used chelating agents EDTA and diethylene triamine pentaacetic acid had similar effects. The addition of superoxide dismutase eliminated the effect of the chelating agents and thus demonstrated that the stimulated reaction was dependent upon O-2. KCN and bathophenanthroline disulfonate, an iron-chelating agent, prevented O-2-dependent NADPH oxidation by neutrophil granule fractions in the presence of EGTA. In contrast, bathocuproine disulfonate, a copper-chelating agent, mimicked the EGTA effect. The effects of both bathophenanthroline disulfonate and bathocuproine disulfonate were completely abolished when the agents were saturated with iron and copper, respectively. All the chelating agents studied, except bathophenonthroline disulfonate, also promoted O-2-dependent NADPH oxidation in a system wherein O-2 was generated by xanthine oxidase. Thus, commonly used chelating agents, by interacting with available iron and copper, may alter the apparent stoichiometry of the neutrophil O-2-generating oxidase and artifactually increase NADPH oxidation in other systems where O-2 is present.
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PMID:Effect of chelating agents and superoxide on human neutrophil NAD(P)H oxidation. 632 25

Xanthine oxidase activity: O2-dependent and NAD+-dependent forms, were carried out in cytosol supernatant of Rat liver homogenat with adjuvant and hepatocytes induced arthritis and hepatitis. Both forms were increased without modification of their ratio. These results suggest that xanthine oxidase was implicated in the inflammatory reaction.
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PMID:[Xanthine oxidase activity: O2-dependent and NAD+-dependent forms in the liver, in rats with adjuvant arthritis and hepatitis]. 640 92

Xanthine oxidase activity: NAD+-dependent form (D) and O2-dependent form (O) were carried out in cytosol supernatants of connective tissue growth (T.C.N.F.), skin tail, liver and plasma of carrageenan induced granuloma in the Rat. The specific activities of skin, liver and plasma were normal in animals with a granuloma. The total specific activity (D + O): 7.53 +/- 0.98 mU/mg protein, and the percentage of form O: 51.6 +/- 5.1 of the granulomatous tissue as compared to the tail are significantly increased. These results suggest the likely function of xanthine oxidase during the inflammatory response.
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PMID:[Xanthine oxidase activity: NAD+-dependent and O2-dependent forms in carrageenan granuloma in the rat]. 642 8

A spectrophotometric method especially suitable for biological materials is described for the determination of purine nucleoside phosphorylase activity. In combination with the enzymes xanthine oxidase, catalase and aldehyde dehydrogenase, and in the presence of ethanol and NAD(P), the purines formed by phosphorylysis of purine nucleosides are oxidized and the absorption of the NAD(P)H formed is taken for the calculation of nucleoside phosphorylase activity.
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PMID:A new spectrophotometric assay for enzymes of purine metabolism. III. Determination of purine nucleoside phosphorylases. 676 4

To further delineate the mechanism responsible for the differences in xanthine oxidase activity in male and female Sprague-Dawley rats, a sensitive and specific radioimmunoassay (RIA) was developed for the measurement of hepatic xanthine oxidase. The RIA could detect as little as 5 mg of liver enzyme. Specificity of the RIA was confirmed by 1) Ouchterlony double immuno-diffusion in which a single precipitin band exhibited xanthine oxidase activity, when crude liver homogenate and an enzyme-specific stain were used; 2) parallelism between purified 125I-labeled xanthine oxidase and serial dilutions of crude liver homogenate; 3) a linear correlation between xanthine oxidase activity and the level of enzyme protein; and 4) a single protein band coincident with purified xanthine oxidase, when an immunoprecipitate prepared from antisera and crude liver homogenate was analyzed on sodium dodecyl sulfate (SDS) polyacrylamide gels. Whether xanthine oxidase activity was assayed in the absence of nicotinamide adenine dinucleotide (NAD+) (oxidase form) or in the presence of NAD+ (dehydrogenase), male values were consistently higher, and both forms of the enzyme correlated significantly with each other. When purified to homogeneity, neither form of the enzyme was appreciably affected by 17 beta-estradiol or testosterone propionate. When the RIA was employed, levels of hepatic xanthine oxidase were significantly greater in male than in female rats. We concluded from these data that increased xanthine oxidase activity in the male corresponds to a greater quantitative complement of xanthine oxidase protein. Furthermore, lower xanthine oxidase activity in the female cannot be explained by immunologically cross-reactive material without enzyme activity nor by a direct sex-steroid enzyme interaction.
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PMID:Quantitation of rat liver xanthine oxidase by radioimmunoassay. A mechanism for sex-specific differences. 689 96

The course of the reaction sequence hypoxanthine leads to xanthine leads to uric acid, catalysed by the NAD+-dependent activity of xanthine oxidoreductase, was investigated under conditions either of immediate oxidation of the NADH formed or of NADH accumulation. The enzymic preparation was obtained from rat liver, and purified 75-fold (as compared with the 25000 g supernatant) on a 5'-AMP-Sepharose 4B column; in this preparation the NAD+-dependent activity accounted for 100% of total xanthine oxidoreductase activity. A spectrophotometric method was developed for continuous measurements of changes in the concentrations of the three purines involved. The time course as well as the effects of the concentrations of enzyme and of hypoxanthine were examined. NADH produced by the enzyme lowered its activity by 50%, resulting in xanthine accumulation and in decreases of uric acid formation and of hypoxanthine utilization. The inhibition of the Xanthine oxidoreductase NAD+-dependent activity by NADH is discussed as a possible factor in the regulation of IMP biosynthesis by the 'de novo' pathway or (from unchanged hypoxanthine) by ther salvage pathway.
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PMID:Effect of NADH on hypoxanthine hydroxylation by native NAD+-dependent xanthine oxidoreductase of rat liver, and the possible biological role of this effect. 695 74

When xanthine oxidase was prepared from fresh raw cow's milk in the presence of dithioerythritol, 94% of its xanthine-oxidizing activity was found as a dehydrogenase type. The enzyme was reversibly converted to an oxidase type when dithioerythritol was removed. The conversion was ascribable to the oxidation of sulfhydryl groups of the enzyme by oxygen. The two forms of the enzyme gave the same visible spectrum, but the dehydrogenase form alone gave a characteristic difference spectrum upon addition of NAD+. NADH served as a good electron donor for the dehydrogenase form of the enzyme but not for the oxidase form. When xanthine was used as an electron donor, the overall rate of p-benzoquinone reduction was the same for the oxidase and dehydrogenase forms, but the proportion of one-electron flux from the enzyme to p-benzoquinone was considerably greater in the reaction of the dehydrogenase form than in that of the oxidase form.
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PMID:Preparation of bovine milk xanthine oxidase as a dehydrogenase form. 695 93


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