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)

Azathioprine (AZA) is cleaved in vivo by glutathione to 6-mercpatopurine (6-MP). 6-MP plasma levels were measured by HPLC in four male rhesus monkeys following oral and iv doses of the two drugs. Following iv 6-MP administration, 6-MP levels were described by a two-compartment body model; mean terminal half-life; plasma clearance (CLp), and volume of distribution (Vdss) were 41.6 +/- 12.1 min, 48.4 +/- 15.4 ml/min/kg, and 1.76 +/- 0.64 liters/kg, respectively. 8-Hydroxymercpatopurine (8-OHMP) was identified as a metabolites of AZA. 8-OHMP had a CLp twice that for 6-MP, while its Vdss was similar to that for 6-MP. After an iv dose, AZA is converted to 6-MP to the extent of 15%. The conversion of AZA to 6-MP and 8-OHMP was independent of the route of administration. Differences in AZA and 6-MP kinetics among the monkeys were attributed to differences in individual aldehyde oxidase and xanthine oxidase levels.
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PMID:Comparative bioavailability and pharmacokinetic studies of azathioprine and 6-mercaptopurine in the rhesus monkey. 4 22

1. The effects of inhibitors and activators on the azo- and nitro-reductases of Ascaris lumbricoides var suum have been investigated. Both types of reduction were inhibited by FAD, FMN, riboflavin, allopurinol, dicoumarol, 5-nitro-2-furaldehyde, azide and cyanide at concentrations of 1 mM. Neither reaction was inhibited by menadione, nitrofurantoin, SKF 525-A or fluoride. Both reactions were stimulated by addition of hypoxanthine. 2. The enzyme preparation contained no detectable aldehyde oxidase or xanthine oxidase activity. 3. The differences in the effects of flavins and inhibitors on mammalian and nematode azo- and nitro-reductases might have practical significance in the development of anthelmintic synergists.
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PMID:The effect of flavins and enzyme inhibitors on 4-nitrobenzoic acid reductase and azo reductase of Ascaris lumbricoides var suum. 5 46

The relationship between allopurinol oxidizing enzyme and aldehyde oxidase was investaged in mice. The oxidation of both N-methylnicotinamide and allopurinol appears to be catalized by a single enzyme, aldehyde oxidase (aldehyde-oxygen oxidoreductase EC, 1.2.3.1.). This conclusion is based on the following evidence; The postnatal changes of allopurinol and N-methylnicotinamide oxidizing activities were similar during growth and the levels of both activities increased in a parallel fashion upon the attainment of sexual maturity. The rates of loss of the activities of both enzymes by heat denaturation as well as dexamethasone administration were similar. The inhibitors of allopurinol oxidizing enzyme also suppressed N-methylnicotinamide oxidation. Competition of N-methylnicotineamide and allopurinol for oxidation was demonstrated. The rate of increase of the activities in both enzymes was almost parallel during each step of the purification from mouse liver supernatant. It was ascertained that xanthine oxidase in the enzyme preparation does not influence allopurinol oxidation.
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PMID:[Hepatic allopurinol oxidizing enzyme in mice]. 12 99

E.p.r- (electron-paramagnetic-resonance) spectroscopy was used to compare chemical environment and reactivity of molybdenum, flavin and iron-sulphur centres in the enzyme xanthine dehydrogenase from Veillonella alcalescens (Micrococcus lactilyticus) with those of the corresponding centres in milk xanthine oxidase. The dehydrogenase is frequently contaminated with small but variable amounts of a species resistant to oxidation and giving a new molybdenum (V) e.p.r. signal, "Resting I". There is also a "desulpho" form of the enzyme giving a Slow Mo(V) signal, indistinguishable from that of the milk enzyme. Molybdenum of the active enzyme behaves in a manner analogous to that of the milk enzyme, giving a Rapid Mo(V) signal on partial reduction with substrates or dithionite. Detailed comparison shows that molybdenum in each enzyme must have the same ligand atoms arranged in the same manner. As with the milk enzyme, complex-formation between reduced dehydrogenase and purine substrate molecules, presumably interacting at the normal substrate-binding site, modifies the Rapid signal, confirming that such substrates interact near molybdenum. The dehydrogenase-flavin semiquinone signal is identical with that of the oxidase but, in contrast, there is only one iron-sulphur signal. The latter gives an e.p.r. spectrum similar to that of aldehyde oxidase.
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PMID:Studies by electron-paramagnetic-resonance spectroscopy on the mechanism of action of xanthine dehydrogenase from Veillonella alcalescens. 17 32

Studies by e.p.r. (electron-paramagnetic-resonance) spectroscopy and by stopped-flow spectrophotometry on turkey liver xanthine dehydrogenase revealed strong similarities to as well as important differences from the Veillonella alcalescens xanthine dehydrogenase and milk xanthine oxidase. The turkey enzyme is contaminated by up to three non-functional forms, giving molybdenum e.p.r. signals designated Resting I, Resting II and Slow. Slow and to a lesser extent Resting I signals are like those from the Veillonella enzyme, whereas Resting II is very like a resting signal described by K. V. Rajagopolan, P. Handler, G. Palmer & H. Beinert (1968) (J. Biol. Chem. 243, 3784-3796) for aldehyde oxidase. Another non-functional form that gives the Inhibited signal is produced on treatment of the enzyme with formaldehyde. Stopped-flow measurements at 450 nm show that, as for the milk enzyme, reduction by xanthine is rate-limiting in enzyme turnover. The active enzyme gives rise to Very Rapid and Rapid molybdenum(V) e.p.r. signals, as well as to an FADH signal. That these signals are almost indistinguishable from those of the milk enzyme, confirms the similarities between the active sites. There are two types of iron-sulphur centres that give signals like those in the milk enzyme, though with slightly different parameters. Quantitative reduction titration of the functional enzyme with xanthine revealed two important differences between the turkey and the milk enzymes. First, the turkey enzyme FADH/FADH2 system has a redox potential sufficiently low that xanthine is incapable of reducing the flavin completely. This finding presumably explains the very low oxidase activity. Secondly, whereas the Fe/S II chromophore in the milk enzyme has a relatively high redox potential, for the turkey enzyme the value of this potential is lower and similar to that of its Fe/S I chromophore.
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PMID:Studies by electron-paramagnetic-resonance spectroscopy and stopped-flow spectrophotometry on the mechanism of action of turkey liver xanthine dehydrogenase. 17 33

A new non-functional modified form of milk xanthine oxidase is described. This contains molybdenum in a quinquivalent state, which is resistant to both oxidation and reduction. The new species is derived from the native enzyme in a two-step process. The first step is the conversion into the desulpho form, via loss of the 'persulphide' sulphur, and the second involves reaction with ethylene glycol or other reagents. The species gives a characteristic Mo(V) electron-paramagnetic-resonance signal, without proton splittings, designated Resting II. This is virtually identical with signals reported previously from resting turkey liver xanthine dehydrogenase and rabbit liver aldehyde oxidase. The possibility is discussed that species Resting II, prepared with ethylene glycol, contains a -COCH2OH residue bound to a nitrogen ligand of molybdenum.
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PMID:A new non-functional form of milk xanthine oxidase containing stable quinquivalent molybdenum. 18 Sep 83

Considerable information is available concerning the oxidation of pteridine derivatives by bovine milk xanthine oxidase, but few investigations have been carried out on the oxidation of such compounds by mammalian liver xanthine oxidase and the related aldehyde oxidase. Xanthine oxidase, obtained from rat liver, oxidizes a variety of substituted amino- and hydroxypteridines in a manner identical to that previously observed for milk xanthine oxidase. For example, 2-aminopteridine and its 4- and 7-hydroxy derivatives were oxidized efficiently to 2-amino-4,7-dihydroxypteridine (isoxanthopterin) by the rat liver enzyme, and 4-aminopteridine and its 2- and 7-hydroxy derivatives were oxidized to 4-amino-2,7-dihydroxypteridine.4-Hydroxypteridine and the isomeric 2- and 7-hydroxypteridines were oxidized by rat liver xanthine oxidase to 2,4,7-trihydroxypteridine. Rabbit liver aldehyde oxidase, but not rat liver xanthine oxidase, was able to catalyze the oxidation in position 7 of 2,4-diaminopteridine and its 6-methyl and 6-hydroxymethyl derivatives. 2-Aminopteridine and 4-aminopteridine were both oxidized to the corresponding 7-hydroxy derivatives in the aldehyde oxidase system; 2-amino-4-hydroxypteridine appeared to be a minor product in the oxidation of 2-aminopteridine by rabbit liver aldehyde oxidase. Both aldehyde oxidase and xanthine oxidase were able to catalyze the oxidation of 2-amino-6,7-disubstituted pteridines to the corresponding 4-hydroxy derivatives; 4-hydroxy-6,7-disubstituted pteridines were oxidized in position 2 by both enzymes. 4-Amino-6,7-disubstituted pteridines were not oxidized by either enzyme. 2-Amino-4-methylpteridine was oxidized in position 7 by aldehyde oxidase but was not an effective substrate for xanthine oxidase; 2-hydroxypteridine and 7-hydroxypteridine were not oxidized to a detectably extent by aldehyde oxidase. All oxidations mediated by xanthine oxidase were strongly inhibited by allopurinol (4-hydroxypyrazolo[3,4-d]pyrimidine), and all oxidations mediated by aldehyde oxidase were inhibited by menadione (2-methyl-1,4-naphthoquinone). Rat liver xanthine oxidase and, to a lesser extent, rabbit liver aldehyde oxidase were inhibited by 4-chloro-6,7-dimethylpteridine; 2-amino-3-pyrazinecarboxylic acid inhibited xanthine oxidase but not aldehyde oxidase. The oxidations of 2- and 4-aminopteridines by aldehyde oxidase resulted in concomitant reduction of cytochrome c.
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PMID:Oxidation of selected pteridine derivatives by mamalian liver xanthine oxidase and aldehyde oxidase. 18 53

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

1. Isoquinoline, cinnoline, quinoxaline, quinazoline and phthalazine were incubated with preparations of rabbit liver aldehyde oxidase. 2. The oxidation products, 1-hydroxyisoquinoline, 4-hydroxycinnoline, 2-hydroxy- and 2,3-dihydroxy-quinoxaline, 4-hydroxy- and 2,4-dihydroxy-quinazoline, and 1-hydroxyphthalazine were identified by comparison of their spectral and chromatographic characteristics with those of authentic compounds. 3. Michaelis-Menten constants are reported for the action of the parent heterocycles with aldehyde oxidase. The compounds reported in this study are among the most efficient substrates yet described for rabbit liver aldehyde oxidase. 4. The compounds in 1 above were incubated with bovine milk xanthine oxidase: only quinazoline and phthalazine yielded significant amounts of metabolites. Km values were calculated for these compounds. 5. Incubation of the heterocycles with rat liver preparations gave qualitatively the same results as those obtained using rabbit liver, but smaller amounts of the oxidation products were detected from rat liver incubations.
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PMID:The oxidation of azaheterocycles with mammalian liver aldehyde oxidase. 51 90

1. Twenty-six strains of mice were surveyed by starch gel electrophoresis for genetic variation of four liver enzymes; aldehyde dehydrogenase, aldehyde oxidase, xanthine oxidase and formaldehyde dehydrogenase. 2. A variant of aldehyde dehydrogenase was found in strains ICFW, IS/Cam, NZB, NZW, Simpson and Schneider. A variant of aldehyde oxidase was found in CE. A possible variant of xanthine oxidase was found in SF/Cam. 3. The gene determining the electrophoretic variant of aldehyde oxidase is either the same as, or very closely linked to, the Aox gene which determines aldehyde oxidase activity.
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PMID:Genetic variation of some aldehyde-oxidizing enzymes in the mouse. 74 39


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