UNIPROT:P47989 - FACTA Search

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Query: UNIPROT:P47989 (xanthine oxidase)
8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of the antioxidant N-acetyl-L-cysteine was studied in a model of polymicrobial sepsis induced in CD-1 mice by cecal ligation and puncture. N-Acetyl-L-cysteine significantly improved survival during the 6 days following sepsis induction and caused lower liver toxicity. This effect was not related to free radicals generated by xanthine oxidase which was significantly induced in liver after cecal ligation and puncture. A specific inhibitor of xanthine oxidase, allopurinol, significantly reduced this enzyme and reduced the early survival rate. The effect of N-acetyl-L-cysteine was not related either to a reduction in tumor necrosis factor production or to a modulation of nitrites or to liver glutathione content. These results show that the induction of xanthine oxidase is not deleterious in this model of sepsis and suggest that N-acetyl-L-cysteine works as a direct antioxidant and scavenger of free radicals generated from other sources.
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PMID:Effect of N-acetyl-L-cysteine on sepsis in mice. 779 76

Heat-shock protein 27 (HSP27) is a major target of phosphorylation upon cell stimulation with a variety of agents and has been suggested to have a phosphorylation-regulated function at the level of actin filaments. Here we investigated comparatively the mechanisms of HSP27 phosphorylation by oxidative stresses, exposures to tumor necrosis factor (TNF), heat shock and growth factors. Extracts of Chinese hamster or human cells exposed to H2O2, xanthine/xanthine oxidase, menadione or TNF contained up to 15-fold more HSP27 kinase activity than comparable extracts obtained from control cells. Induction of HSP27 kinase activity by TNF or H2O2 was completely inhibited by first treating the cells with the antioxidant N-acetyl-L-cysteine, suggesting that generation of reactive oxygen metabolites was the key triggering element of this induction. In contrast, prior treatment with acetylcysteine had no or little effect on the induction by thrombin, serum and heat shock. The kinase activity in extracts of cells stimulated by heat shock, H2O2, sodium arsenite, TNF or growth factors was identified by in-gel renaturation and purified approximately 8000-fold by sequential chromatography. In all cases, the induced kinase activity was entirely associated with two polypeptides of 45 kDa and 54 kDa, identified as mitogen-activated-protein kinase-activated protein (MAPKAP) kinase-2 based on its reactivation in vitro by 42/44-kDa MAP kinases, its antigenic properties and its substrate specificity. The 45/54-kDa HSP27 kinase may play an important role in the cell response to oxidative stress. Overexpression of the wild-type HSP27 but not of a nonphosphorylatable form of human HSP27 in Chinese hamster cells conferred resistance to actin fragmentation by oxidative stress generated by H2O2. It is concluded that activation of the 45/54-kDa HSP27 kinase is a common mechanism of HSP27 phosphorylation to which converge both oxyradical-dependent and oxyradical-independent pathways and which may participate in a homeostatic response to stress at the level of actin microfilament.
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PMID:Characterization of 45-kDa/54-kDa HSP27 kinase, a stress-sensitive kinase which may activate the phosphorylation-dependent protective function of mammalian 27-kDa heat-shock protein HSP27. 785 16

Chondrocytes stimulated with IL-1 produce high levels of nitric oxide (NO), which inhibits proliferation induced by transforming growth factor-beta or serum. This study analyzes the role of NO and IL-1 in the induction of chondrocyte cell death. NO generated from sodium nitroprusside induced apoptosis in cultured chondrocytes as demonstrated by electron microscopy, 4',6-dianidino-2-phenylindole dihydrochloride staining, FACS analysis, and histochemical detection of DNA fragmentation. Similar results were obtained with two other NO donors, 3-morpholinosynonimide-hydrochloride and s-nitroso-N-acetyl-D-L-penicillamine. In contrast, oxygen radicals generated by hypoxanthine/xanthine oxidase caused necrosis but did not induce chondrocyte apoptosis. To analyze whether endogenously generated NO induces apoptosis, chondrocytes were stimulated with IL-1, but there was no evidence for apoptotic changes. Combinations of NO inducers such as IL-1, lipopolysaccharide, tumor necrosis factor, and interferon-gamma also failed to trigger apoptosis. IL-1-stimulated chondrocytes are known to produce oxygen radicals that react with NO to form products that can induce cell death in other systems. We thus tested IL-1 in combination with the oxygen radical scavengers N-acetyl cysteine, dimethyl sulfoxide, or 5,5'-dimetylpyrroline 1-oxide. Under these conditions IL-1 was able to induce apoptosis, which was inhibited in a dose-dependent manner by the NO synthase inhibitor N-monomethyl L-arginine. Conversely, endogenous oxygen radicals induced by inflammatory mediators caused necrosis under conditions in which the simultaneous production of NO was reduced. These results suggest that NO, but not oxygen radicals, is the primary inducer of apoptosis in human articular chondrocytes.
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PMID:Chondrocyte apoptosis induced by nitric oxide. 785 40

The dimethylsulphoxide reductase of Rhodobacter capsulatus contains a pterin molybdenum cofactor molecule as its only prosthetic group. Kinetic studies were consistent with re-oxidation of the enzyme being rate limiting in the turnover of dimethylsulphoxide in the presence of the benzyl viologen radical. EPR spectra of molybdenum(V) were generated by reducing the highly purified enzyme under a variety of conditions, and with careful control it was possible to generate at least five clearly distinct EPR signals. These could be simulated, indicating that each corresponds to a single chemical species. Structures of the signal-giving species are discussed in light of the EPR parameters and of information from the literature. Three of the signals show coupling of molybdenum to an exchangeable proton and, in the corresponding species, the metal is presumed to bear a hydroxyl ligand. One signal with gav 1.96 shows a very strong similarity to a signal for the desulpho form of xanthine oxidase, while two others with gav values of 1.98 show a distinct similarity to signals from nitrate reductase of Escherichia coli. These data indicate an unusual flexibility in the active site of dimethylsulphoxide reductase, as well as emphasising structural similarities between molybdenum enzymes bearing different forms of the pterin cofactor. Interchange among the different species must involve either a change of coordination geometry, a ligand exchange, or both. The latter may involve replacement of an amino acid residue co-ordinating molybdenum via O or N, for a cysteine co-ordinating via S. Since the two signals with gav 1.96 were obtained only under specific conditions of reduction of the enzyme by dithionite, it is postulated that their generation may be triggered by reduction of the pteridine of the molybdenum cofactor from a dihydro state to the tetrahydro state.
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PMID:Multiple states of the molybdenum centre of dimethylsulphoxide reductase from Rhodobacter capsulatus revealed by EPR spectroscopy. 792 52

The conditions under which nitric oxide (.NO) may modulate or promote lung injury have not been identified. We hypothesized that .NO-induced injury results from peroxynitrite, formed by the reaction of .NO with superoxide. The simultaneous generation of .NO and superoxide by 3-morpholinosydnonimine (SIN-1, 0.1-2 mM) resulted in oxidation of dihydrorhodamine, a marker of peroxynitrite production, and a dose-dependent decrease in the ability of SP-A to enhance lipid aggregation. Western blot analysis of SIN-1 exposed SP-A samples, overlaid with a polyclonal antibody against nitrotyrosine, were consistent with nitration of SP-A tyrosine residues. Superoxide dismutase (100 U/ml), L-cysteine (5 mM), xanthine oxidase (10 mU/ml) and xanthine (500 microM), or urate (100 microM) prevented the SIN-1-induced dihydrorhodamine oxidation and injury to SP-A. .NO alone, generated by S-nitroso-N-acetylpenicillamine plus 100 microM L-cysteine, or superoxide and hydrogen peroxide, generated by pterin and xanthine oxidase in the absence of iron, did not damage SP-A or oxidize dihydrorhodamine. We concluded that peroxynitrite, but not .NO or superoxide and hydrogen peroxide, in concentrations likely to be encountered in vivo, caused nitrotyrosine formation and decreased the ability of SP-A to aggregate lipids.
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PMID:Concurrent generation of nitric oxide and superoxide damages surfactant protein A. 794 50

Vitamin K3 (menadione), a synthetic vitamin K congener, inhibits the growth of tumor cells. Here, we examined possible effects of vitamin K3 on phospholipase D (PLD) activity, an enzyme which produces growth regulatory substances. In NIH 3T3 fibroblasts, vitamin K3 (50-100 microM) alone had no effect on PLD-catalyzed formation of phosphatidylethanol, a marker of PLD activity, but it slightly (10-21%) inhibited the stimulatory effect of phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC). Of the two major substrates of PLD, phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn), vitamin K3 (10-100 microM) preferentially inhibited PtdEtn hydrolysis when stimulated by PMA or platelet-derived growth factor, the latter being a hormonal activator of PKC. Vitamin K3 had no inhibitory effect on sphingosine- or staurosporine-induced hydrolysis of PtdEtn or PtdCho. Inhibition of PMA-induced PtdEtn hydrolysis by vitamin K3 was effectively reduced by both cysteine (1 mM) and reduced glutathione (1 mM) and was mimicked by the superoxide-generating xanthine/xanthine oxidase system. The results show that vitamin K3 preferentially inhibits the effects of PKC activators on PLD-mediated hydrolysis of PtdEtn by a mechanism which may involve oxidation of thiols in a critically important regulatory component.
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PMID:Vitamin K3 preferentially inhibits stimulation of phospholipase D-mediated hydrolysis of phosphatidylethanolamine by protein kinase C activators in NIH 3T3 fibroblasts. 794 97

Recent findings have suggested that nitric oxide (NO) reacts with superoxide anion (O2-) to form a potential oxidant, peroxynitrite anion, which then decays to hydroxyl radical and nitrogen dioxide. In order to ascertain this hypothesis in human polymorphonuclear leukocytes (PMNs) which release both NO and O2-, we studied oxidation of L-cysteine (CYS) and bovine serum albumin (BSA) by PMNs and cell-free O2(-)-generating system of hypoxanthine (HX)-xanthine oxidase (XO) reaction. Oxidation of CYS by HX-XO was equally inhibited by superoxide dismutase (SOD) and catalase (CAT), and that of BSA by HX-XO was inhibited weakly by SOD and strongly by CAT. PMNs stimulated with phorbol 12-myristate 13-acetate increased the oxidation rates of CYS and BSA, and they were inhibited by SOD and CAT almost in a similar way to those by HX-XO. The NO synthase inhibitor, NG-monomethyl-L-arginine (NMMA), was confirmed to have an inhibitory effect on the inhibition of platelet aggregation by PMNs, and L-arginine (ARG) reversed this effect. However, pretreatment of PMNs with either of NMMA, or ARG, or both did not change the oxidation rates of CYS and BSA. We could not confirm the hypothesis at least in human PMNs that interaction of NO with O2- forms powerful oxidants to sulfhydryls of CYS and BSA. These results suggest that oxidation of sulfhydryls of CYS and BSA by PMNs is primarily dependent on reactive oxygen species, and is not modified by NO production.
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PMID:Nitric oxide does not contribute to superoxide-mediated sulfhydryl oxidation in human polymorphonuclear leukocytes. 803 64

Using a lysosome-enriched "light mitochondrial" fraction of a rat liver homogenate, the effects of the reactive oxygen species hydrogen peroxide, superoxide- and hydroxyl radicals were determined. Alterations in the intralysosomal pH and the release of a lysosomal marker enzyme, N-acetyl-glucosaminidase, were used as indicators of changes in the lysosomal membrane integrity. Lipid peroxidation of the fraction was assayed by TBARS measurement. Neither superoxide radicals, generated by hypoxanthine/xanthine oxidase, nor a bolus dose of hydrogen peroxide (0.5-1.5 mM) induced any lysosomal damage. If, however, Fe(III)ADP was included in the superoxide radical-generating system, lysosomal membrane damage was detected, both as an increase in lysosomal pH and as a release of N-acetyl-glucosaminidase, but only after a lag phase of about 7 min. Lipid peroxidation, on the other hand, proceeded gradually. Lysosomes treated with hydrogen peroxide displayed similar dose-dependent alterations, albeit only if both Fe(III)ADP and the reducing amino acid cysteine were added. In the latter system, however, alterations of the lysosomal membrane stability occurred more rapidly, showing a lag phase of only 2 min. Lipid peroxidation, which proceeded faster and displayed no lag phase, levelled out within 10 min. The results indicate that neither superoxide radicals nor hydrogen peroxide are by themselves damaging to lysosomes. Available catalytically active iron in Fe(II) form, however, allows reactions yielding powerful oxidative species--probably hydroxyl radicals formed via Fenton reactions--to take place inducing peroxidation of the lysosomal membranes resulting in dissipation of the proton-gradient and leakage of their enzyme contents.
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PMID:Effect of reactive oxygen species on lysosomal membrane integrity. A study on a lysosomal fraction. 814 62

This study looks at the role of xanthine oxidase (XO) in ischemia/reperfusion (I/R) induced intestinal mucosal damage using normal and xanthine oxidase deficient rats. Tungstate feeding for 3 days depleted the intestinal mucosal XO by 80%. A ligated loop of the rat small intestine (both normal and XO-deficient) was subjected to 1 h of total ischemia followed by 5 min revascularisation. The ensuing mucosal damage was assessed by biochemical and histological studies. Ischemia or I/R increased the XO levels in normal rats without any change in XO-deficient rats. Myeloperoxidase (a neutrophil marker) level was increased in both group of rats but it was comparatively higher in the XO-deficient rats. Accumulation of peroxidation products such as malondialdehyde, conjugated diene and increased production of hydroxyl radicals by microsomes were seen after ischemia and I/R and were similar in normal and XO-deficient rats. Studies on other parameters of peroxidation showed a decrease in polyunsaturated fatty acids and alpha-tocopherol, an increase in cysteine and cystine levels after I/R and were similar in both normal and XO-deficient rats. Histological results indicated gross morphological changes in the intestinal mucosa due to ischemia and I/R, and the damage was more severe in XO-deficient rats. These observations suggest that oxygen-derived free radicals are involved in the intestinal mucosal damage during I/R and infiltrated neutrophils rather than XO may be the primary source of free radicals under these conditions.
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PMID:Oxygen free radical induced damage during intestinal ischemia/reperfusion in normal and xanthine oxidase deficient rats. 823 77

We isolated cDNAs encoding xanthine dehydrogenase (XD; xanthine:NAD+ oxidoreductase, EC 1.1.1.204) from a human liver cDNA library. The complete nucleotide sequence of human XD was determined; the deduced amino acid sequence encoded a protein of 1336 amino acid residues of M(r) 147,782. Human XD possessed many of the signature sequences typical of XDs from flies and rodents, including an unusual cysteine distribution, a potential 2Fe/2S binding site, and a putative molybdopterin cofactor binding domain. Analysis of potential NAD binding sites suggested a simple hypothesis for the conversion of human XD into the oxygen metabolite forming xanthine oxidase (XO; xanthine:oxygen oxidoreductase, EC 1.1.3.22). Using a human XD complementary RNA hybridization probe, we found a 5100-base RNA in human liver by RNA blot-hybridization analysis. This RNA exhibited tissue-specific distribution that may be pertinent to XD- and XO-mediated oxygen radical injury in ischemia/reperfusion and inflammation. A second 4500-base RNA was detected in some tissues and may arise through differential transcription termination.
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PMID:cDNA cloning, characterization, and tissue-specific expression of human xanthine dehydrogenase/xanthine oxidase. 824 61

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