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 superoxide-dismutase-like activity of a series of divalent metal saccharinates of general stoichiometry [MII(Sac)2(H2O)4].2H2O (with MII = Mn,Fe,Co,Ni,Cu,Zn) has been investigated using the nitroblue tetrazolium O2- reduction assay. The results show that all these complexes possess the capability to dismutate the superoxide anion generated in the xanthine/xanthine oxidase system. Interestingly, the greatest activity is shown by the corresponding copper complex. The results are discussed and compared with those obtained for native superoxide dismutase, which was tested under the same experimental conditions.
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PMID:Determination of superoxide dismutase-like activity in some divalent metal saccharinates. 768 41

The effects of Zn, Mg, Cr, Cu, and Mn aspartates, their commercial formulation Inzolen, and the individual commercial medicine Unizinc, on oxygen radical production by enzymes [xanthine oxidase, horseradish peroxidase, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase] and phagocytic cells (human blood leukocytes) have been studied. The formation of oxygen radicals was measured by luminol- and lucigenin-amplified chemiluminescence and by the reduction of cytochrome c. All these compounds (excluding Cr aspartate) turn out to be inhibitors of oxygen radical formation in the systems studied (excluding horseradish peroxidase). Their inhibitory activities were a consequence of both the scavenging of free radicals and the inhibition of xanthine oxidase and NADPH oxidase activities. As expected, the most active free-radical scavengers were transition metal Cu and Mn aspartates, which mimicked the activities of copper-zinc and manganese dismutases. However, surprisingly non-transition metal Zn and Mg aspartates were also able to scavenge oxygen radicals. It was suggested that the scavenging activities of Zn and Mg aspartates may be explained by affecting the rate of spontaneous dismutation of the superoxide ion. In addition, it was found that Zn aspartate is an efficient inhibitor of the formation of the most reactive hydroxyl radicals. These antioxidant properties of Zn aspartate make it important in medicine for the prevention and treatment of free radical pathologies.
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PMID:Study of antioxidant properties of metal aspartates. 774 Dec 42

The Onchocerca volvulus superoxide dismutase was expressed in Escherichia coli, using a protocol designed to produce the native enzyme rather than a fusion protein. The recombinant O. volvulus superoxide dismutase (rOVSOD) was found in the cytosol of the disrupted bacteria and represented > 10% of the total bacterial protein. The enzyme was purified to homogeneity using DEAE-Sepharose chromatography, followed by phenyl-Sepharose chromatography. The rOVSOD was enzymatically active which was demonstrated by its reactivity with O2.- produced either by the xanthine-xanthine oxidase system or by stimulated eosinophils. The specific activity was determined to be 4668 U mg-1. This activity could be blocked by rabbit antiserum raised against the rOVSOD. The maximal activity was obtained upon supplementation of the bacterial growth media and enzyme buffer with copper and zinc ions. Activity characteristics in the presence of inhibitors was also characteristic of a Cu/Zn superoxide dismutase. The rOVSOD has an apparent subunit molecular mass of 16,000 in SDS-PAGE. The active enzyme behaves as a dimer of 32 kDa as determined by gel filtration.
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PMID:Characterization of enzymatically active Onchocerca volvulus Cu/Zn superoxide dismutase expressed in Escherichia coli. 783 82

The reactivity and toxicity of nitric oxide is modest in comparison to oxidants derived from nitric oxide. Exposure of Escherichia coli to 1 mM nitric oxide under aerobic or anaerobic conditions did not decrease viability of the bacteria. Peroxynitrite (1 mM), the reaction product of superoxide and nitric oxide, was completely bactericidal after 5 s. The nitrovasodilator, 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1), slowly decomposes to release both nitric oxide and superoxide and thereby produces peroxynitrite. SIN-1 killed E. coli in direct proportion to its concentration with an LD50 of 0.5 mM. Copper, zinc superoxide dismutase (50-400 units/ml) provided substantial but not complete protection against SIN-1 killing. Catalase (500-10,000 units/ml) partially protected in direct proportion to its concentration, while inactivated catalase was not protective. Superoxide dismutase and catalase together completely protected E. coli against SIN-1 toxicity. Oxy-hemoglobin eliminated both SIN-1 and peroxynitrite toxicity. The bactericidal activity of SIN-1 was further enhanced by pterin plus xanthine oxidase. Pterin plus xanthine oxidase alone or together with Fe3+ ethylenediamine tetraacetate produced no significant decrease in E. coli viability. Hydrogen peroxide was not directly toxic to the bacteria, but E. coli pretreated with hydrogen peroxide were more susceptible to peroxynitrite, SIN-1, and the aerobic oxidation products of nitric oxide. Hydrogen peroxide pretreatment did not increase significantly the toxicity of nitric oxide under anaerobic conditions. Our results suggest that peroxynitrite is far more toxic to E. coli than nitric oxide or its by products from aerobic oxidation.
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PMID:The comparative toxicity of nitric oxide and peroxynitrite to Escherichia coli. 784 Jun 33

Previous studies have shown that susceptibilities of hepatocytes and endothelial cells to H2O(2)-induced injury are altered by changes in the intracellular activity of Cu,Zn-containing superoxide dismutase (CuZn-SOD). To evaluate the role of intracellular CuZn-SOD in oxidant-induced injury to rat cardiac myocytes, cells with reduced CuZn-SOD activity but normal ATP content were either isolated from the hearts of adult copper-deficient rats or obtained by treatment of normal isolated adult myocytes with diethyldithiocarbamate. These myocytes and controls with normal CuZn-SOD activity were exposed to either reagent H2O2 or oxidants generated by extracellular glucose oxidase plus glucose or xanthine oxidase plus xanthine. It was shown that myocytes with CuZn-SOD activities reduced by 70-90% were equally susceptible to H2O2 and the two oxidant-generating systems as the control myocytes. The findings suggest that in adult cardiac myocytes, in contrast to the situation in some other cells, intracellular CuZn-SOD may not have a significant defensive role against acute H2O(2)-induced injury. The possibility remains, however, that changes in the activity of this enzyme, e.g., in copper deficiency, may be relevant to the ability of myocytes to cope with chronic oxidative stress resulting from imbalance between intracellular oxygen radical-generating and -scavenging systems.
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PMID:Role of intracellular SOD in oxidant-induced injury to normal and copper-deficient cardiac myocytes. 790 Aug 65

Effects of Cu2+,Zn2+,Fe2+ and selenium ions on the conversion of xanthine dehydrogenase to oxidase in rabbit liver were examined. Under basal conditions, xanthine oxidase activity represented only 16% of the total xanthine oxidase plus dehydrogenase activity. Cu2+ (2-10 microM), Zn2+ (5-30 microM) and selenium ions (5-100 microM) brought about the conversion of xanthine dehydrogenase to oxidase in a dose-dependent manner. The concentrations of Cu2+,Zn2+ and selenium ions required for increasing xanthine oxidase activity by 50% was approximately 4, 10 and 20 microM, respectively. On the other hand, Fe2+ had no effect on the conversion of the enzyme up to 100 microM. These results suggest that Cu2+,Zn2+ and selenium ions have the potential to modulate the conversion of xanthine dehydrogenase to oxidase in rabbit liver.
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PMID:Induction of the conversion of xanthine dehydrogenase to oxidase in rabbit liver by Cu2+,Zn2+ and selenium ions. 793 44

The objective of this study was to investigate whether quin2, through its metal chelating properties, could affect copper- or iron-driven Fenton reactions. Chelation of ferric ion with quin2 uniformly strongly enhanced the formation of oxidizing species, detected with the DMSO and deoxyribose assays, both by H2O2 and a mixture of superoxide/hydrogen peroxide produced by hypoxanthine/xanthine oxidase. Fe(3+)-EDTA gave the same effects, but lacked reactivity with bolus H2O2 as detected with the DMSO assay. Whereas the formation of oxidizing species with Fe(3+)-EDTA and ferric ions alone were strongly inhibited by superoxide dismutase both in the bolus H2O2 and hypoxanthine/xanthine oxidase systems, such formation in the presence of Fe(3+)-quin2 either did not decrease or decreased only moderately. Fe(3+)-quin2 also strongly enhanced plasmid DNA strand breakage in the presence of H2O2. Our findings suggest that quin2 as chelator of ferric ion may be a more powerful enhancer of oxidant formation than other chelators so far tested. The formation of oxidizing species from copper ions and bolus H2O2 was found to be fundamentally dependent on the choice of buffer system. We could only detect significant amounts of oxidants in both assays in Hepes buffer, but not in the phosphate, cacodylate or unbuffered systems, which all gave low reactivity in the DMSO assay compared to the deoxyribose assay. Quin2 chelation of cupric ion effectively inhibited the formation of oxidants as well as plasmid DNA strand breakage.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:New roles for quin2: powerful transition-metal ion chelator that inhibits copper-, but potentiates iron-driven, Fenton-type reactions. 800 13

The presence of superoxide dismutase (SOD) activity in the bovine lungworm Dictyocaulus viviparus was examined using the xanthine-xanthine oxidase assay system and by non-denaturing PAGE followed by specific enzyme staining. High levels of activity were detected in excretory-secretory (ES) products of adult worms and in soluble extracts of both the L3 and adult stages of the parasite. Stage-specific and ES-specific activities were indicated by differences in SOD isoenzyme profiles between adult and larval parasite extracts and between adult extract and ES products, with a fast migrating activity being specific to ES products. All isoenzymes were sensitive to cyanide, indicating copper/zinc dependency. The antigenicity of ES SOD was demonstrated by a reduction in SOD activity in both the chemical assay and non-denaturing PAGE following incubation of parasite ES products with IgG antibody purified from serum of infected or vaccinated bovine hosts. The high level of SOD activity released by adult D. viviparus may be a reflection of the problems faced by a parasite occupying an oxygen-rich environment. Antibody inhibition of SOD may, therefore, be an important target of protective immunity.
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PMID:Superoxide dismutase (SOD) activity of Dictyocaulus viviparus and its inhibition by antibody from infected and vaccinated bovine hosts. 808 70

To determine the effect of oxidative stress on expression of extracellular superoxide dismutase (EC-SOD), CuZn-SOD and Mn-SOD, two fibroblast lines were exposed for periods of up to 4 days to a wide concentration range of oxidizing agents: xanthine oxidase plus hypoxanthine, paraquat, pyrogallol, alpha-naphthoflavone, hydroquinone, catechol, Fe2+ ions, Cu2+ ions, buthionine sulphoximine, diethylmaleate, t-butyl hydroperoxide, cumene hydroperoxide, selenite, citiolone and high oxygen partial pressure. The cell lines were cultured both under serum starvation and at a serum concentration that permitted growth. Under no condition was there any evidence of EC-SOD induction. Instead, the agents uniformly, dose-dependently and continuously reduced EC-SOD expression. We interpret the effect to be due to toxicity. Enhancement of the protection against oxidative stress by addition of CuZn-SOD, catalase and low concentrations of selenite did not influence the expression of any of the SOD isoenzymes. Removal of EC-SOD from cell surfaces by heparin also did not influence SOD expression. Mn-SOD was moderately induced by high doses of the first 11 oxidants. Apart from reduction at high toxic doses, there were no significant effects on the CuZn-SOD activity by any of the treatments. Thus EC-SOD, previously shown to be profoundly influenced by inflammatory cytokines, was not induced by its substrate or other oxidants. In a similar fashion, Mn-SOD, previously shown to be greatly induced and depressed by cytokines, was only moderately influenced by oxidants. We suggest that the regulation of these SOD isoenzymes in mammalian tissues primarily occurs in a manner co-ordinated by cytokines, rather than as a response of individual cells to oxidants.
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PMID:Effects of oxidative stress on expression of extracellular superoxide dismutase, CuZn-superoxide dismutase and Mn-superoxide dismutase in human dermal fibroblasts. 813 41

Oxidative modification of low density lipoprotein (LDL) has been suggested as a causal step in atherosclerosis, and both redox-active transition metal ions and superoxide (O2.-) have been implicated in this process. In order to determine the mechanisms of metal ion-dependent oxidation of LDL in the presence of O2.-, LDL was exposed to hypoxanthine (HX) and purified xanthine oxidase (XO) without and with added CuCl2 or Fe(3+)-citrate. Production of O2.- and hydrogen peroxide (H2O2) at pH 7.4 by the HX/XO system in the absence of metal ions was not sufficient to oxidize LDL. Preincubation of LDL with Cu2+ or Fe(3+)-citrate with subsequent removal of metal ions not tightly bound to the lipoprotein did not enable the HX/XO system to oxidize LDL. However, incubation of LDL with HX/XO and Cu2+ resulted in extensive modification of LDL. Exposure of LDL to Cu2+ alone also led to extensive modification, although the LDL was initially free of detectable amounts of lipid hydroperoxides (LOOH), i.e., < 0.005 molecules of LOOH per LDL particle. Although HX/XO and Cu2+ did not produce detectable amounts of O2.- or aqueous hydroxyl radicals (HO.), oxidation of LDL under these conditions was partially inhibited by superoxide dismutase, and completely inhibited by the HO. scavenger thiourea. In contrast to Cu(2+)-mediated oxidation of LDL, oxidation mediated by Fe(3+)-citrate was strictly dependent upon O2.-, as it was abolished by omission of the HX/XO system or by addition of superoxide dismutase to this system.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanisms of copper- and iron-dependent oxidative modification of human low density lipoprotein. 824 25


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