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)

Senescent cell antigen (SCANT) is a "neo antigen" that appears on the surface of normal old cells and initiates IgG binding and cellular removal. To investigate the mechanism by which SCANT is generated from its parent molecule, band 3, we subjected intact human erythrocytes to treatments that have been reported to result in changes in band 3 and/or to mimick aging in vitro. The validity of these treatments as model systems for erythrocyte aging was evaluated using a "red cell aging panel" that provides a biochemical profile of a senescent red cell. Treatments were assessed for their ability to induce in vitro the following changes observed in normal erythrocytes aged in vivo: 1 increased breakdown of band 3 as detected by immunoblotting, 2 decrease in anion transport efficiency as detected with a sulfate self-exchange assay, 3 decrease in total glyceraldehyde 3-phosphate dehydrogenase activity with an increase in membrane-bound activity, and 4 increase in the binding of autologous IgG as detected with a protein A binding assay. Neither incubation with the free radical-generating xanthine oxidase/xanthine system, nor treatment with malondialdehyde, and end product of free radical-initiated lipid (per)oxidation, results in age-specific changes. Loading of the cells with calcium and oxidation with iodate results in increased breakdown of band 3, but does not lead to increased binding of autologous IgG. Only erythrocytes that have been stored for 3-4 weeks show the same structural and functional changes as observed during aging in vivo.
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PMID:Erythrocyte aging: a comparison of model systems for simulating cellular aging in vitro. 317 56

1. The catalytic properties of xanthine oxidase in bovine milk (EC 1.2.3.2) are dependent on the state of the enzyme, i.e. whether free or bound to the fat-globule membrane. Oxidase activity of the membrane-bound enzyme towards NADH is enhanced relative to that towards xanthine. This reflects a change in the relative K(m) values and enables the ratio of xanthine to NADH oxidase activities (X/N) to be used as a parameter for the relative amounts of free and membrane-bound xanthine oxidase in milk fractions. 2. Chromatography of buttermilk on Sepharose 2B yielded an excluded fraction, BM(1), with xanthine oxidase activity. The remaining xanthine oxidase activity was eluted as a single broad peak. This was further resolved on Sephadex G-200 into an excluded fraction, BM(2), and free xanthine oxidase. Fractions BM(1) and BM(2) had X/N values in the range 45-65, which is characteristic of membrane-bound xanthine oxidase. Purified xanthine oxidase has a mean X/N value of 110.3. Addition of fraction BM(1), heated to remove associated enzyme activities, to purified xanthine oxidase progressively enhanced its NADH oxidase activity to a value where its X/N value was characteristic of membrane-bound xanthine oxidase. This was shown to be due to binding of free enzyme to heated fraction BM(1). The binding constant and stoicheiometry were determined. 4. Proteolytic digestion of fraction BM(1) liberated free xanthine oxidase from the fat-globule membrane with a corresponding alteration in X/N value.
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PMID:Association of xanthine oxidase with the bovine milk-fat-globule membrane. 415 54

t-Butyl alcohol is not a substrate for alcohol dehydrogenase or for the peroxidatic activity of catalase and, therefore, it is used frequently as an example of a non-metabolizable alcohol. t-Butyl alcohol is, however, a scavenger of the hydroxyl radical. The current report demonstrates that t-butyl alcohol can be oxidized to formaldehyde plus acetone by hydroxyl radicals generated from four different systems. The systems studied were: (a) two chemical systems, namely, the iron catalyzed oxidation of ascorbic acid and the Fenton reaction between H2O2 and iron; (b) an enzymatic system, the coupled oxidation of xanthine by xanthine oxidase; and (c) a membrane-bound system, NADPH-dependent microsomal electron transfer. The oxidation of t-butyl alcohol appeared to be mediated by hydroxyl radicals, or by a species with the oxidizing power of the hydroxyl radical, because the production of formaldehyde plus acetone was (a) inhibited by competing scavengers of the hydroxyl radical; (b) stimulated by the addition of iron-EDTA; and (c) inhibited by catalase. The last observation suggests that H2O2 served as the precursor of the hydroxyl radical in all three systems. A possible mechanism is hydrogen abstraction to form the alkoxyl radical [CH3)3-C-O.), spontaneous fission of the alkoxyl radical to produce acetone and the methyl radical (CH3.), interaction of the methyl radical with O2 to form the methyl peroxy radical (CH300.), and decomposition of the later to formaldehyde. These results extend the alcohol oxidizing capacity of the microsomal alcohol oxidizing system to a tertiary alcohol. Since t-butyl alcohol is not a substrate for alcohol dehydrogenase or catalase, the ability of microsomes to oxidize t-butyl alcohol lends further support for a role for hydroxyl radicals in the microsomal alcohol oxidation system. In view of the production of formaldehyde, and the reactivity as well as further metabolism of this aldehyde, caution should be used in interpreting experiments in which t-butyl alcohol is used as a presumed "non-metabolizable" alcohol. t-Butyl alcohol may be a valuable probe for the detection of hydroxyl radicals in intact cells and in vivo.
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PMID:Production of formaldehyde and acetone by hydroxyl-radical generating systems during the metabolism of tertiary butyl alcohol. 631 86

Guinea-pig mammary tissue was perfused in vitro, radiolabelled with [35S]methionine and intracellular protein precursors of the milk-fat-globule membrane (FGM) recovered by immunoabsorption techniques. Labelled xanthine oxidase was solely detected in post-microsomal supernatants and butyrophilin in carbonate-washed membranes. A major glycoprotein (Gp 55), was initially present in a membrane-bound form, but after longer perfusion times a fraction of this protein was recovered in the post-microsomal supernatant. These results are discussed with reference to formation of the apically-derived FGM.
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PMID:Protein synthesis in lactating guinea-pig mammary tissue perfused in vitro. II. Biogenesis of milk-fat-globule membrane proteins. 653 41

The effect of cold storage (5 C, 24 h) and heat treatment (60 C, 5 min) of milk on activities of free and membrane-bound xanthine oxidase has been studied. Both treatments enhanced total xanthine oxidase activity in milk. Activity of membrane-bound xanthine oxidase increased and free xanthine oxidase decreased in buttermilk while it increased in skim milk on cold storage. Heat of milk increased free and membrane-bound xanthine oxidase activities in both buttermilk and skim milk. The state of xanthine oxidase activity in skim milk from reconstituted milk, which was prepared by mixing xanthine oxidase inactivated skim milk and fresh cream, showed that only the free enzyme migrated from the cream phase to skim milk on cold storage. Very little xanthine oxidase activity was detectable in skim milk on heat treatment of the reconstituted milk sample. The overall increased activity of xanthine oxidase in milk during cold storage or heat treatment may not be due to the release of fat globule membrane enzyme to skim milk.
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PMID:Free and membrane-bound xanthine oxidase in bovine milk during cooling and heating. 689 20

Biochemical studies have demonstrated that dihydroorotate dehydrogenase (DHOdehase; EC 1.3.3.1 or 1.3.99.11) is the sole enzyme of de novo pyrimidine synthesis in mitochondria, whereas the rest of the pathway takes place in the cytosol. The dehydrogenation of dihydroorotate to orotate is linked to the respiratory chain via ubiquinone. In this study, we show for the first time the ultrastructural localization of DHOdehase. Since the purified enzyme was found to act both as dehydrogenase and as oxidase, the cerium capture technique for detecting enzymatically generated hydrogen peroxide could be applied to pin-point the in situ activity of DHOdehase oxidase in mitochondria of rat heart and kidney cortex. Cerium perhydroxide as the final reaction product was detected predominantly in the matrix with some focal condensation along the inner membrane, but not in the intermembrane space. From this pattern of localization, it is concluded that the active site of the membrane-bound enzyme could face the mitochondrial matrix similar to succinate dehydrogenase. The reliability of the applied method for the demonstration of DHOdehase oxidase was demonstrated by the addition of Brequinar sodium to the incubation medium. This quinoline-carboxylic acid derivative is a potent inhibitor of DHOdehase and has proven anti-proliferative activity. The present observations do not ascertain whether the oxidase is permanently active as a constant portion of the enzyme in vivo, similar to xanthine oxidase/dehydrogenase. However, DHOdehase should be considered as a source of radical oxygen species under pathophysiological conditions.
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PMID:Localization of dihydroorotate oxidase in myocardium and kidney cortex of the rat. An electron microscopic study using the cerium technique. 764 4

Using the human erythroleukaemic cell line K562 cl.6 and its daunorubicin-resistant subline K/DAU600, and the human T-lymphoblastic leukaemic cell line CCRF-CEM and its vinblastine-resistant subline CEM/VLB100, we have shown that the drug-resistant cell lines were more sensitive to cytotoxicity induced by tumour necrosis factor-alpha (TNF alpha). Drug-resistant cell lines showed increased activities of copper/zinc superoxide dismutase (Cu/ZnSOD) and catalase compared with their parental drug-sensitive cell lines. However, the greater susceptibility of drug-resistant cells to TNF alpha cytotoxicity was, in part, related to their decreased activities of manganese superoxide dismutase (MnSOD). Persistence of this differential sensitivity when MnSOD is inhibited by sodium nitroprusside (SNP) suggests that the greater susceptibility of drug-resistant cells to TNF alpha was not entirely due to their decreased level of MnSOD activity. K562 cl.6 and K/DAU600, which were more resistant to TNF alpha, both expressed greater levels of endogenous plasma membrane-bound TNF alpha than the CCRF-CEM cell line. All cell lines examined were (more or less) equal in susceptibility to the cytolytic effect of exogenous O2-. generated by xanthine/xanthine oxidase. These results demonstrate that both MnSOD and endogenous TNF alpha play a role in protecting leukaemic cells against TNF alpha cytotoxicity, but there is an unknown mechanism that causes drug-resistant cells to be more susceptible to TNF alpha cytotoxicity.
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PMID:TNF-mediated killing of human leukaemic cells: effects of endogenous antioxidant levels and TNF alpha expression in leukaemic cell lines. 770 80

Human erythrocytes were oxidized with xanthine/xanthine oxidase/ferric ion or ADP/ferric ion at 37 degrees C for several hours. Band 3 protein and spectrin of the oxidized cells were found to be significantly modified as analyzed by radiolabeling with tritiated borohydride. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of the xanthine/xanthine oxidase/ferric iron-oxidized cells and subsequent immunoblotting with anti band 3 protein showed that band 3 protein was fragmented into smaller molecular-weight fragments. When the cell membrane obtained from the oxidized cells were incubated at pH 7.4 and 37 degrees C for several hours in the presence of alpha-tocopherol, extensive degradation of band 3 protein and spectrin was observed. Band 3 protein was found to be most susceptible to the degradation. Degradation of band 3 protein was also observed after similar incubation of the membrane from the ADP/ferric ion-oxidized cells. Membrane-bound serine- and metalloproteinases were responsible for the degradation of band 3 protein, because the degradation was remarkably inhibited by diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride, and partially by ethylenediaminetetraacetic acid. Hence, the membrane proteins became susceptible to membrane-bound proteinases by oxidative stress. This observation suggests that these membrane-bound proteinases exist to remove oxidatively damaged proteins from the cell membrane.
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PMID:Presence of membrane-bound proteinases that preferentially degrade oxidatively damaged erythrocyte membrane proteins as secondary antioxidant defense. 798 14

The potential involvement of reactive oxygen species in the expression of genes involved in immune response was examined in mesangial cells. Tumor necrosis factor (TNF-alpha) and aggregated (aggr.) IgG increased mRNA levels for the monocyte chemoattractant protein, JE/MCP-1, and the colony-stimulating factor, CSF-1. Scavengers for free radicals such as di- and tetra-methylthiourea (DMTU and TMTU) attenuated the increase in mRNA levels in response to TNF-alpha and aggr. IgG. Generation of superoxide anion by xanthine oxidase and hypoxanthine increased mRNA levels of these genes, but exogenous H2O2 did not. Addition of NADPH to activate a membrane-bound NADPH-oxidase generated superoxide and caused a dose-dependent increase in mRNA levels and further enhanced the stimulation by TNF-alpha or aggr. IgG. An inhibitor of NADPH-dependent oxidase 4'-hydroxy-3'-methoxy-acetophenone attenuated the rise in mRNA levels in response to TNF-alpha and aggr. IgG. By nuclear run-on experiments TNF-alpha, aggr. IgG and NADPH increased the transcription rates for JE/MCP-1 and CSF-1, effects inhibited by TMTU. We conclude that generation of reactive oxygen species, possibly by NADPH-dependent oxidase, are involved in the induction of the JE/MCP-1 and CSF-1 genes by TNF-alpha and IgG complexes. The concerted expression of leukocyte-directed cytokines represents a general response to tissue injury.
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PMID:Oxygen radicals as second messengers for expression of the monocyte chemoattractant protein, JE/MCP-1, and the monocyte colony-stimulating factor, CSF-1, in response to tumor necrosis factor-alpha and immunoglobulin G. Evidence for involvement of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent oxidase. 839 28

Reactive oxygen species (ROS) play an important role in the pathogenesis of ischemia-reperfusion injury. Extracellular H2O2 generation from bovine pulmonary artery endothelial cells (EC) is known to increase in response to anoxia-reoxygenation (A-R). To determine potential sources of intracellular ROS formation in EC in response to A-R, a fluorometric assay based on the oxidation of 2',7'-dichlorofluorescin was used. Intracellular ROS production declined 40% during 6 h of anoxia (P < 0.05). After A-R, the rates of intracellular ROS formation increased to 148 +/- 9% (P < 0.001) that of normoxic EC (100 +/- 3%). In EC exposed to A-R, allopurinol and NG-methyl-L-arginine (L-NMMA), inhibitors of xanthine oxidase (XO) and nitric oxide synthase (NOS), respectively, reduced intracellular ROS formation by 25 +/- 1% (P < 0.001) and 36 +/- 4% (P < 0.01). Furthermore, at low doses (i.e., 20 microM), deferoxamine and diethylenetriaminepentaacetic acid (DTPA) significantly inhibited intracellular ROS formation. However, at 100 microM, only deferoxamine caused further reduction in DCF fluorescence. In summary, EC respond to A-R by generating increased amounts of XO- and NOS-derived intracellular ROS. The inhibition, to a similar extent, caused by allopurinol and L-NMMA, as well as the effect of deferoxamine and DTPA suggest that the ROS detected is peroxynitrite. Based on these findings and previous work, we conclude that EC generate ROS in response to A-R from at least two different sources: a plasma membrane-bound NADPH oxidase-like enzyme that releases H2O2 extracellularly and XO, which generates intracellular O2-, which in turn may react with nitric oxide to form peroxynitrite.
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PMID:Intracellular generation of reactive oxygen species in endothelial cells exposed to anoxia-reoxygenation. 917 54


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