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)

A protein fraction, which did not contain NADP [or NADPH]-dependent aldehyde reductase as well as NAD [or NADP]-dependent aldehyde dehydrogenases, but which catalyzed oxidation of fatty-aromatic aldehydes, was isolated from extract of rat liver tissue using ammonium sulfate fractionation combined with gradient syvorptive chromatography on DEAE-Sephadex A-25 [or Molselect DEAE-25], CM-Sephadex C-25 and gel-filtration on Sephadex G-200. Investigations of molecular weight and catalytic properties of the protein fraction obtained enabled to identify it with xanthine oxidase [EC 1.2.3.2]. Aldehyde dehydrogenases as well as xanthine oxidase are involved in oxidation of fatty-aromatic aldehydes to corresponding fatty acids, besides the reduction of the aldehydes to alcohols, catalyzed by aldehyde reductase and alcohol dehydrogenases.
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PMID:[Oxidation of fatty-aromatic aldehydes in liver tissues]. 3 12

A method to purify bovine liver xanthine oxidase in described, with which samples of 256-fold specific activity with respect to the initial homogenate are obtained. Bovine liver xanthine oxidase and chicken liver xanthine dehydrogenase with oxygen as electron acceptor exhibit similar profile in pKM and log V versus pH plots. With NAD+ as electron acceptor a different profile in the pKM xanthine plot is obtained for chicken liver xanthine dehydrogenase. However three inflection points at the same pH values appear in all plots. Both enzymes are irreversibly inhibited by pCMB and reversibly by N-ethylmaleimide and by iodoacetamide, with competitive and uncompetitive type inhibitions respectively. These results suggest that NAD+ alters the enzymatic action since its binding to the enzyme antecedes the binding of xanthine to the xanthine oxidase molecule, without undergoing itself any modification. 0.15 M DDT of DTE treatment of bovine liver xanthine oxidase gives to the enzyme a permanent activity with NAD+ without modifying its activity with oxygen. The enzyme thus treated produces parallel straight lines in Lineweaver-Burk plots.
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PMID:[Comparative study of chicken liver xanthine dehydrogenase and bovine liver xanthine oxidase. dehydrogenase activity of xanthine oxidase (author's transl)]. 3 57

A spectrophotometric method for the determination of three forms of xanthine oxidoreductase, namely dehydrogenase (D), dehydrogenase-oxidase (D/O) and oxidase (O), is described. Enzymic fractions obtained from rat liver were found to contain either all three forms, or (under special conditions of preparation) only two forms, D and D/O. The conversion of form D leads to form D/O leads to form O in the presence of Cu2+ ions was shown. Form D/O acted with NAD+ as well as with O2 as electron acceptors, it exhibited greater affinity to NAD+ than to O2, and NAD+ abolished the oxidase activity of this form. Moreover, oxidase activity of form D/O was inhibited by NADH. These facts indicate that NAD+ and O2 compete for the same active site on the enzyme molecule.
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PMID:Intermediate dehydrogenase-oxidase form of xanthine oxidoreductase in rat liver. 22 81

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 phase and mitochondrial, and 2-naphthyl laurate hydrolase microsomal and/or brush border. 3. Histochemistry confirmed the use of alkaline phosphatase and 1-naphthyl acetate esterase as brush border and microsome markers respectively. 4. Urate oxidase, allantoinase, allantoicase, xanthine oxidase and glycollate/lactate oxidase, activities were undetectable, and 1-naphthyl palmitate hydrolase was present only as a contaminant from pancreas.
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PMID:Intestinal peroxisomes of goldfish (Carassius auratus)--examination for hydrolase, dehydrogenase and carnitine acetyltransferase activities. 31 95

1. Cellulose acetate zymograms of alcohol dehydrogenase (ADH), aldehyde dehydrogenase, sorbitol dehydrogenase, aldehyde oxidase, "phenazine" oxidase and xanthine oxidase extracted from tissues of inbred mice were examined. 2. ADH isozymes were differentially distributed in mouse tissues: A2--liver, kidney, adrenals and intestine; B2--all tissues examined; C2--stomach, adrenals, epididymis, ovary, uterus, lung. 3. Two NAD+-specific aldehyde dehydrogenase isozymes were observed in liver and kidney and differentially distributed in other tissues. Alcohol dehydrogenase, aldehyde oxidase, "phenazine" oxidase and xanthine oxidase were also stained when aldehyde dehydrogenase was being examined. 4. Two aldehyde oxidase isozymes exhibited highest activities in liver. 5. "Phenazine oxidase" was widely distributed in mouse tissues whereas xanthine oxidase exhibited highest activity in intestine and liver extracts. 6. Genetic variants for ADH-C2 established its identity with a second form of sorbitol dehydrogenase observed in stomach and other tissues. The major sorbitol dehydrogenase was found in high activity in liver, kidney, pancreas and male reproductive tissues.
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PMID:Electrophoretic analyses of alcohol dehydrogenase, aldehyde dehydrogenase, aldehyde oxidase, sorbitol dehydrogenase and xanthine oxidase from mouse tissues. 31 79

Xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) supplemented with an electron donor could catalyze the cis-trans isomerization of 3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide, 3-(5-nitro-2-furyl)-2-phenylacrylamide and 3-(5-nitro-2-furyl)-2-(2-furyl)acrylonitrile. The direction of isomerization (cis leads to trans, cis in equilibrium trans or trans leads to cis) is dependent on the chemical structure of these nitrofuran derivatives. Lipoyl dehydrogenase (NADH:lipoamide oxidereductase, EC 1.6.4.3), DT-diaphorase (NAD(P)H:(quinone-acceptor) oxidoreductase, EC 1.6.99.2) and liver microsomes could also catalyze the conversion of cis-3-(5-nitro-2-furyl)-2-(2-furyl)acrylamide to its trans isomer in the presence of an appropriate electron donor. Such isomerizing activity of these enzymes is much higher than their nitro-reducing activity. In addition, the cis-trans isomerization of some nitrofuran derivatives was demonstrated with the liver slices and the small intestines of rats. A new cis-trans isomerization mechanism which is based on transfer of a single electron by an enzyme system to a nitrofuran derivative to give the radical-anion was proposed. This postulated mechanism was supported by the preliminary experiments using pulse radiolysis technique.
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PMID:Enzymic cis-trans isomerization of nitrofuran derivatives: isomerizing activity of xanthine oxidase, lipoyl dehydrogenase, DT-diaphorase and liver microsomes. 45 30

A new method for the determination of xanthine oxidase activity with xanthine or hypoxanthine is described. The hydrogen peroxide produced by the oxidation of the substrates is reduced by catalase in the presence of high concentrations of ethanol. The acetaldehyde formed is further oxidized by aldehyde dehydrogenase NAD or NADP-dependent. The reduction rate of the coenzymes were measured at 334 nm and utilized as indicators for the xanthine oxidase. The sensitivity of the method with xanthine as substrate can be doubled by the addition of uricase, which oxidizes uric acid to allantoin.
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PMID:A new spectrophotometric assay for enzymes of purine metabolism. I. Determination of xanthine oxidase activity. 48 56

A new method for the determination of guanase is described. Xanthine, the product of the guanase reaction, is oxidized by xanthine oxidase, forming uric acid and hydrogen peroxide. Hydrogen peroxide is further reduced to water by catalase in the presence of ethanol. The acetaldehyde formed in this reaction step is dehydrogenated NAD or NADP dependent by aldehyde dehydrogenase. The NADH or NADPH production is measured and utilized for the calculation of the guanase activity. The sensitivity of the method can be doubled by the addition of uricase, which oxidizes uric acid to permit the formation of another mole of hydrogen peroxide.
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PMID:A new spectrophotometric assay for enzymes of purine metabolism. II. Determination of guanase activity. 48 57

Redox potentials for the various centres in the enzyme xanthine dehydrogenase (EC 1.2.1.37) from turkey liver determined by potentiometric titration in the presence of mediator dyes, with low-temperature electron-paramagnetic-resonance spectroscopy. Values at 25 degrees C in pyrophosphate buffer, pH 8.2, are: Mo(VI)/Mo(V)(Rapid),-350 +/- 20mV; Mo(V) (Rapid)/Mo(IV), -362 +/- 20mV; Fe-S Iox./Fe-S Ired., -295 +/- 15mV; Fe-S IIox./Fe-S IIred., -292 +/- 15mV; FAD/FADH,-359+-20mV; FADH/FADH2, -366 +/- 20mV. This value of the FADH/FADH2 potential, which is 130mV lower than the corresponding one for milk xanthine oxidase [Cammack, Barber & Bray (1976) Biochem. J. 157, 469-478], accounts for many of the differences between the two enzymes. When allowance is made for some interference by desulpho enzyme, then differences in the enzymes' behaviour in titration with xanthine [Barber, Bray, Lowe & Coughlan (1976) Biochem. J. 153, 297-307] are accounted for by the potentials. Increases in the molybdenum potentials of the enzymes caused by the binding of uric acid are discussed. Though the potential of uric acid/xanthine (-440mV) is favourable for full reduction of the dehydrogenase, nevertheless, during turnover, for kinetic reasons, only FADH and very little FADH2 is produced from it. Since only FADH2 is expected to react with O2, lack of oxidase activity by the dehydrogenase is explained. Reactivity of the two enzymes with NAD+ as electron acceptor is discussed in relation to the potentials.
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PMID:Oxidation--reduction potentials of turkey liver xanthine dehydrogenase and the origins of oxidase and dehydrogenase behaviour in molybdenum-containing hydroxylases. 86 27

Milk xanthine oxidase (XO) has been prepared in a dehydrogenase form (XDH) by purifying the enzyme in the presence of 2.5 mM dithiothreitol. Unlike XO, which reacts rapidly only with oxygen and not with NAD, the XDH form of the enzyme reacts rapidly with NAD. XDH has a turnover number for the NAD-dependent conversion of xanthine to urate of 380 mol/min/mol at pH 7.5, 25 degrees C, with a Km = < or = 1 microM for xanthine and a Km = 7 microM for NAD, but has very little O2-dependent activity. There is evidence that the two forms of the enzyme have different flavin environments: XDH stabilizes the neutral form of the flavin semiquinone and XO does not. Further, XDH binds the artificial flavin 8-mercapto-FAD in its neutral form, shifting the pK of this flavin by 5 pH units, while XO binds 8-mercapto-FAD in its benzoquinoid anionic form. XDH can be converted back to the XO form by the addition of three to four equivalents of the disulfide-forming reagent 4,4'-dithiodipyridine, suggesting that, in the XDH form of the enzyme, disulfide bonds are broken; this may cause a conformational change which creates a binding site for NAD and changes the protein structure near the flavin.
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PMID:Purification and properties of milk xanthine dehydrogenase. 132 33


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