Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of the xenobiotic metabolizing enzymes, aldehyde oxidase and xanthine oxidase, were determined in partially purified fractions of adult guinea-pig liver at given times in the day or night. A marked circadian variation in aldehyde oxidase activity was observed with several substrates (phthalazine, phenanthridine, N-phenylquinolinium and 3,4-dihydro-4-hydroxy-3-methyl-2-quinazolinone). The main peak occurred at 0300 hr with minimum activity from 1200 to 1800 hr, the differences between rhythmic extremes being statistically significant (P less than 0.005). Xanthine oxidase activity also exhibited a daily rhythm but with a lower amplitude. Guinea-pig serum melatonin showed a synchronous circadian fluctuation with peak values at 0300 hr falling throughout the day to a minimum at 1800 hr. Exogenously administered melatonin caused a significant increase in aldehyde oxidase activity at 0900 and 1200 hr and in xanthine oxidase activity at 0900 hr. It was concluded that melatonin concentrations may be related to the circadian variation in liver molybdenum hydroxylase activity.
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PMID:Diurnal variation and melatonin induction of hepatic molybdenum hydroxylase activity in the guinea-pig. 271 20

In anaesthetized rats 50% of an infused dose of methotrexate (MTX) was excreted into the bile. About 3% was metabolized to 7-hydroxymethotrexate (7-OH-MTX), which appeared also in the bile. Pretreatment with allopurinol had no influence on the elimination of MTX or the production of 7-OH-MTX during a 3-h infusion of MTX. Cyanamide decreased the total MTX clearance, but increased the biliary elimination of 7-OH-MTX. Phorone decreased the biliary MTX-clearance, but not the biliary secretion of 7-OH-MTX. The results show that neither aldehyde oxidase nor xanthine oxidase is the predominant hydroxylating enzyme for MTX in the rat.
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PMID:No influence of enzyme inhibitors on the hydroxylation of methotrexate in rats. 281 3

Reactive oxygen metabolites (ROMs) are partially reduced oxygen species that include superoxide, hydrogen peroxide, hydroxyl radical, and hypohalous acids. Formation of superoxide or hydrogen peroxide may be injurious to tissue directly; however, it is thought that the primary mediators of tissue damage are the secondarily derived oxidants such as hydroxyl radical and hypohalous acid. The gastrointestinal tract is particularly well endowed with the enzymatic machinery necessary to form large amounts of ROMs. Sources of ROMs in the gastrointestinal tract include mucosal oxidases such as xanthine oxidase, amine oxidase, and aldehyde oxidase as well as the NADPH oxidase found in the resident phagocytic leukocytes (macrophages, neutrophils, eosinophils) of the lamina propria. We have demonstrated that reperfusion of ischemic small intestine results in substantial mucosal injury that is mediated by oxy radicals generated from xanthine oxidase and inflammatory leukocytes. The final mediator of toxicity appears to be the hydroxyl radical derived from the iron-catalyzed interaction between superoxide and hydrogen peroxide. Data from our laboratories as well as other laboratories suggest that reactive oxygen metabolites may play an important role in mediating mucosal injury during active episodes of ulcerative colitis. We present a working hypothesis which states that transient ischemic episodes in the bowel initiate a cascade of self-perpetuating cycles of ROM formation, inflammation and, ultimately, mucosal injury.
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PMID:Neutrophil-mediated mucosal injury. Role of reactive oxygen metabolites. 283 Oct 16

Chromate was reduced during the oxidation of 1-methylnicotinamide chloride by partially purified rabbit liver aldehyde oxidase. In addition to 1-methylnicotinamide, several other electron donor substrates for aldehyde oxidase were able to support the enzymatic chromate reduction. The reduction required the presence of both enzyme and the electron donor substrate. The rate of the chromate reduction was retarded by inhibitors of aldehyde oxidase but was not affected by substrates or inhibitors of xanthine oxidase. These results are consistent with the involvement of aldehyde oxidase in the reduction of chromate by rabbit liver cytosolic enzyme preparations.
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PMID:Chromate reduction by rabbit liver aldehyde oxidase. 294 Oct 18

We have investigated the nitroreduction of the 2-nitroimidazole benznidazole (BENZO) to its corresponding amine by murine normal tissues and tumours. In vivo concentrations of BENZO and its amine metabolite were measured by HPLC 3 hr after BENZO, 2.5 mmoles kg-1 i.p. This gave plasma and tissue BENZO concentrations of 96-160 micrograms ml-1 or g-1. Mouse plasma, KHT and RIF-1 tumour BENZO amine concentrations were very low (0.3-1.4 micrograms g-1); kidney and EMT6 tumours had intermediate levels; and liver contained very high amine levels (approximately 50 micrograms g-1). Three per cent of the BENZO dose was recovered as amine in the 24 hr urine, compared to 5% for the parent compound. Nitroreduction to the amine was demonstrated with liver and tumour preparations under N2 in vitro. The reaction was highly dependent on NADPH, and inhibited extensively in air. With liver microsomes and whole homogenates 2 and 3 moles respectively of BENZO were consumed per mole of amine formed. Inhibitor studies showed that NADPH: cytochrome P-450 (cytochrome c) reductase and cytochrome P-450 were both involved in BENZO reduction, predominantly at early and late reduction steps respectively. Aldehyde oxidase contributed to the cytosolic nitroreduction. Purified buttermilk xanthine oxidase also reduced BENZO to its amine under anaerobic conditions in vitro, but very inefficiently. The apparent Km and Vmax for BENZO amine production by whole liver homogenates were 0.148 mM and 1.45 nmole min-1 mg-1 protein respectively. Tumour homogenates were less active than liver; e.g. Vmax for the KHT tumour was 6-10-fold lower.
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PMID:Nitroimidazole bioreductive metabolism. Quantitation and characterisation of mouse tissue benznidazole nitroreductases in vivo and in vitro. 310 39

The activity of the molybdenum hydroxylase, aldehyde oxidase, was determined in crude homogenates and (NH4)2SO4 fractions prepared from guinea pig liver, lung, kidney, intestine, spleen and heart. Xanthine oxidase was also measured in (NH4)2SO4 fractions. In each case, xanthine oxidase levels were lower than those of aldehyde oxidase; activity of the latter enzyme was highest in the liver, whereas xanthine oxidase was predominant in the small intestine. There was no significant difference in the activity of either molybdenum hydroxylase between tissues taken from male and female guinea pigs.
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PMID:Tissue distribution of the molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase, in male and female guinea pigs. 344 90

Isoelectric focusing (IEF) and cellulose acetate electrophoresis were used to examine the multiplicity and distribution of aldehyde dehydrogenases (ALDHs), aldehyde oxidase (AOX) and xanthine oxidase (XOX) from tissues of olive and yellow baboons. Five ALDHs were resolved and distinguished on the basis of their differential tissue and subcellular distribution or substrate specificity. Some ALDHs exhibited multiple activity zones. Baboon liver ALDHs were differentially distributed in cytosol (ALDHs II, III and V) and large granular (mitochondrial) fractions (ALDHs I and IV). The major liver ALDHs (I and II) were also broadly distributed in other tissues, as was the major stomach enzyme (ALDH-III). Three brain ALDHs were resolved, which were also differentially distributed between large granular (mitochondrial) (ALDHs I and IV) and cytosolic (ALDH-III) fractions. Electrophoretic variability between individuals was observed for the major liver mitochondrial isozyme (ALDH-I), the major stomach isozyme (ALDH-III) and the minor liver isozymes (ALDHs IV and V). Single forms of AOX and XOX were found in baboon tissue extracts, with the highest activities in liver (AOX) and intestine extracts (XOX). Both oxidases were predominantly localized in the liver soluble fraction.
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PMID:Aldehyde dehydrogenases, aldehyde oxidase and xanthine oxidase from baboon tissues: phenotypic variability and subcellular distribution in liver and brain. 375 5

The stabilized carbonium ion salt, tropylium tetrafluoroborate, was oxidized to tropone (cycloheptatrienone) by rabbit liver aldehyde oxidase but not by the closely related molybdenum hydroxylase, xanthine oxidase. The tropylium cation is an aromatic hydrocarbon which lacks the aldehyde, imine, or iminium functional groups present in other substrates of aldehyde oxidase. The unique structural features of the tropylium ion should make it a useful tool for mechanistic studies of aldehyde oxidase.
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PMID:Tropylium tetrafluoroborate, a novel substrate for aldehyde oxidase. 377 70

1-Amino- and 1-chlorophthalazine were tested for possible substrate activity with partially purified rabbit-liver aldehyde oxidase and bovine-milk xanthine oxidase. 1-Chlorophthalazine was a more efficient substrate than the parent compound, phthalazine, with either aldehyde oxidase or xanthine oxidase. The oxidation product of 1-chlorophthalazine was identified as 4-chloro-1-(2H)-phthalazinone on the basis of chromatographic, infra-red and mass-spectral data. 1-Aminophthalazine was oxidized by aldehyde oxidase to 4-amino-1-(2H)-phthalazinone but was a competitive inhibitor of xanthine oxidase. Kinetic studies at different pH values indicated that, in each case, it is the unprotonated form of 1-aminophthalazine that reacts with the molybdenum hydroxylases.
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PMID:Reaction of 1-amino- and 1-chlorophthalazine with mammalian molybdenum hydroxylases in vitro. 382 75

The mechanism of the enhancing effect of methyl viologen (MV) and flavin-adenine dinucleotide (FAD) on sulfoxide reduction which is mediated by a combination of aldehyde oxidase (AO) from guinea pig liver and one-electron reducing flavoenzymes, such as milk xanthine oxidase (XO), was examined. The activity of anaerobic reduction of diphenyl sulfoxide (DPSO) to diphenyl sulfide (DPS) was less than 1 nmol/min/mg protein of AO preparation in a system consisting of hypoxanthine, XO and AO. However, the sulfoxide reduction by this system was enhanced about 6- and 100-fold by the additions of FAD and MV, respectively. In the system containing MV or FAD, other one-electron reducing flavoenzymes such as nicotinamide adenine dinucleotide (reduced form) (NADH) dehydrogenase, lipoamide dehydrogenase and glutathione reductase with an appropriate electron donor, could replace XO. The ability of supplemented flavoenzymes to facilitate DPSO reduction correlated with their abilities to reduce MV and FAD. When AO was omitted from the combined system, no sulfoxide reduction was observed. Stoichiometric study revealed that MV semiquinone and FADH2 were oxidized at ratios of 2 and 1 mol, respectively, per mol of DPS formed. These results indicate that either MV or FAD serves as an electron carrier from the supplemented flavoenzymes to AO, a terminal reductase of sulfoxide.
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PMID:Sulfoxide reduction catalyzed by guinea pig liver aldehyde oxidase in combination with one-electron reducing flavoenzymes. 383 63


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