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)

Heme-nonapeptide inhibits NADH and NADPH dependent lipid peroxidation of brain microsomes in the presence or absence of ADP-Fe complex. The transient accumulation of lipid peroxides during NADH or NADPH dependent, ADP-Fe stimulated lipid peroxidation, is inhibited by heme-nonapeptide. Oxygen consumption of brain microsomes in the presence of NADH or NADPH is stimulated by heme-nonapeptide. Reduction of cytochrome-c and nitro-tetrazolium-blue by O2- generated by xanthine oxidase is inhibited by heme-nonapeptide.
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PMID:Effect of a heme-peptide derived from cytochrome-c on lipid peroxidation. I. Effects on brain microsomes. 302 27

Citrate-Fe3+, reportedly a physiological chelate, exhibits superoxide dismutaselike activity, as evidenced by the inhibition of xanthine oxidase-dependent cytochrome c reduction; the dismutation of xanthine oxidase-generated superoxide to hydrogen peroxide and oxygen, and the enhanced disproportionation of potassium superoxide. The catalytic activity of citrate-Fe3+ corresponds, on a molar basis, to 0.03% of that of copper- and zinc-containing superoxide dismutase. Although weak, this activity enables citrate-Fe3+ to inhibit superoxide and ADP-Fe3+ -dependent peroxidation of extracted microsomal lipids. Also, the dismutase activity of citrate-Fe3+ interferes with its ability to promote lipid peroxidation. It is proposed that chelation of Fe3+ by citrate may represent a protective mechanism against the deleterious consequences of superoxide generation.
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PMID:Superoxide-dependent redox cycling of citrate-Fe3+: evidence for a superoxide dismutaselike activity. 302 73

The potential for iron bound to transferrin to be released and promote the peroxidation of phospholipid liposomes was investigated using ADP as a low molecular weight chelator and superoxide generated by the xanthine/xanthine oxidase system as the reducing agent. Lipid peroxidation in this system was dependent upon transferrin as the source of iron; increasing the transferrin concentration resulted in increased rates of lipid peroxidation. Increasing the xanthine oxidase activity also caused increased rates of peroxidation. Catalase stimulated rates of peroxidation at all xanthine oxidase activities tested. Conditions resulting in the most rapid release of iron from transferrin (low pH, high ADP) did not promote the greatest rates of lipid peroxidation, indicating that at neutral pH, rates of lipid peroxidation may be limited by the availability of iron. It is concluded that transferrin is not a likely source of iron for catalysis of deleterious biological oxidations such as lipid peroxidation in vivo.
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PMID:Transferrin-dependent lipid peroxidation. 302 12

Radical scavenging action of tinoridine, a non-steroidal anti-inflammatory drug with a potent anti-peroxidative activity, was investigated. Tinoridine reduced a stable free radical, diphenyl-p-picryl-hydrazyl, in the molar ratio of about 1:2, indicating its free radical scavenging ability. Tinoridine inhibited the lipid peroxidation in rat liver microsomes induced by xanthine-xanthine oxidase system in the presence of ADP and Fe2+, in which hydroxyl radical (. OH) is formed. Tinoridine was demonstrated to be oxidized in the course of the lipid peroxidation by following the fluorescence derived from the oxidation product of tinoridine. It was also oxidized by the xanthine-xanthine oxidase system in the presence of Fe2+, but its oxidation was slow in the absence of Fe2+ and almost completely inhibited by catalase. Tinoridine was also oxidized by H2O2-Fe2+ system producing . OH (Fenton reaction), but it did not affect the reduction of cytochrome c caused by superoxide radical. These results indicate that tinoridine is able to scavenge . OH and the main active oxygen species responsible for the lipid peroxidation is . OH. The anti-peroxidative and . OH scavenging ability of tinoridine should contribute to its anti-inflammatory action.
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PMID:Hydroxyl radical scavenging action of tinoridine. 303 74

The present experiments were conducted to determine whether endothelium-dependent relaxation is impaired in chronic (10-12 wk), streptozotocin-induced diabetic rat aortas and to determine the specificity and sensitivity of diabetic vasculature to oxygen-derived free radicals. Endothelium-dependent relaxation by acetylcholine and ADP was severely impaired in diabetic rat aorta, whereas endothelium-independent relaxation by nitroglycerin or papaverine was not impaired. Exposure to a free radical-generating system of xanthine plus xanthine oxidase caused a marked and prolonged relaxation in diabetic but not control vessels. Relaxation could not be prevented by the cyclooxygenase inhibitor indomethacin or the lipoxygenase inhibitor nordihydroguaiaretic acid but was attenuated or blocked by catalase. After free radical exposure, aortic rings were washed, reequilibrated, and contracted with a submaximal concentration of norepinephrine. In free radical-exposed vessels, endothelium-dependent relaxation by acetylcholine was reduced by 50% in nondiabetic vessels and abolished in diabetic vessels. Nevertheless, diabetic vessels could still be fully relaxed by nitroglycerin or papaverine. These results suggest selective impairment of endothelium-dependent relaxation in chronic diabetic rat aortas with particular sensitivity to free radical-induced damage.
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PMID:Oxygen free radicals abolish endothelium-dependent relaxation in diabetic rat aorta. 314 Jun 77

Xanthine oxidase increases the rate of actin polymerization. This occurs at oxidase concentrations as low as 40 nM provided the concentration of the polymerizing agent is low (0.5 mM MgCl2). In the presence of 0.1 M KCl plus 1 mM MgCl2 as the polymerizing agents, xanthine oxidase does not affect the rate of the polymerization but increases significantly the rate of the conversion of F(ATP)actin into F(ADP.Pi)actin and probably also the rate of the orthophosphate release.
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PMID:On the interaction between xanthine oxidase and actin. 319 Jul 22

The evidence is convincing that oxidants and agents which induce a cellular pro-oxidant state can act as carcinogens, in particular as promoters and progressors. Importantly, infiltrated phagocytes represent a source of oxidants in inflamed tissues. We have studied the mechanism of the promotional action of active oxygen (AO) in mouse epidermal cells JB6 by comparing the non-promotable clone 30 to the promotable clone 41. In order to mimick AO released by phagocytes we used xanthine/xanthine oxidase as a source of extracellular superoxide and hydrogen peroxide. We found that AO stimulated the growth only of promotable clone 41 after an initial period of moderate inhibition while it was strongly cytostatic for non-promotable clone 30. Reasons for the higher cytostatic effect of AO on the non-promotable clone 30 were discovered when we measured DNA strand breakage and poly ADP-ribosylation of chromosomal proteins. At equal doses AO induced 4-5 times more DNA breaks in clone 30 in reactions which required iron--and probably also calcium--ions. The higher amount of DNA breakage in clone 30 was reflected in a higher extent of poly ADP-ribosylation. Excessive DNA breakage and poly ADP-ribosylation which causes the depletion of NAD and ATP may be responsible for the strong cytostatic effect of AO in clone 30. We conclude that differential resistance to the cytostatic/cytotoxic effect of AO in part determines the promotability of mouse epidermal cells JB6.
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PMID:Active oxygen induced DNA strand breakage and poly ADP-ribosylation in promotable and non-promotable JB6 mouse epidermal cells. 333 7

The lipid peroxidation process is enhanced in both hyperoxygenated or underoxygenated tissues though its mechanism of production is different. Because in thyroid functional diseases there are severe disorders in tissue oxygenation we studied the lipid peroxidation process by using the serum level of malondialdehyde (MDA) as indicator. We also determined the serum ceruloplasmin (CP), an enzymatic protein belonging to the circulating system of antioxidative protection and also playing a role in the cell-mediated immunity. We also followed serum level of uric acid (UA). The determinations were performed on serum samples collected from three groups: 1, adult control subjects: 2. adult untreated hyperthyroid patients, and 3. adult hypothyroid thyroidectomized patients to whom replacement therapy was discontinued for at least 15 days. The mean MDA level was significantly higher in both hyperthyroid and hypothyroid patients by comparison to the control group. CP mean level was significantly lower than in controls. It was concluded that in post thyroidectomy hypothyroidism an enhancement of lipid peroxidation does exist and that its consequences are probably aggravated by the low serum CP level. The enhancement of the process occurs by other mechanisms than for hyperthyroid group. At hypothyroid patients there is an ADP excess which is degenerated to xanthine, the substrate of xanthine oxidase resulting in toxic anion superoxide and UA. In contrast with hyperthyroid group, in hypothyroid patients we observed significant higher values of UA in comparison to the controls. The excess of MDA found in hyperthyroid patients is statistically significant, but its consequences are probably less severe because the serum CP is higher than normal, a rather expected finding for an autoimmune disease.
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PMID:Significance of high levels of serum malonyl dialdehyde (MDA) and ceruloplasmin (CP) in hyper- and hypothyroidism. 338 87

The abilities of pig liver (copper, zinc) metallothionein I and rat liver zinc metallothionein II to modify lipid peroxidation in incubations of liver microsomes have been compared with the activities of reduced glutathione, mannitol, quinacrine, EDTA, dimethyl-pyrroline-N-oxide and phenyl-butyl-nitrone. Lipid peroxidation was determined by assay of thiobarbituric acid reactive substance formation in incubations of microsomes with iron/ADP or a mixture of xanthine and xanthine oxidase. Zinc metallothionein II had no effect on the extent of peroxidation in either system but (copper, zinc) metallothionein I caused a stimulation of peroxidation initiated by xanthine and xanthine oxidase, all other compounds tested were inhibitory. Gel exclusion chromatography of incubations of (copper, zinc) metallothionein I with xanthine and xanthine oxidase revealed aggregation of the metalloprotein. This may have exposed copper in a form capable of initiating peroxidation.
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PMID:Stimulation of peroxidation in rat liver microsomes by (copper, zinc)-metallothioneins. 350 92

We applied a sensitive, precise liquid-chromatographic method of analysis for inosine, hypoxanthine, and xanthine to the study of fructose metabolism in humans and in rats. In the rat, intravenous loading with fructose induced, within minutes, substantial increases in the concentrations of inosine, hypoxanthine, and xanthine in plasma and urine. In plasma, these concentrations peaked after 5 min, then practically disappeared within 10 min. As expected, the fructose-induced increase in hypoxanthine was greatly amplified by pretreating the rats with allopurinol, an inhibitor of xanthine oxidase. In a healthy human subject, intravenous administration of fructose also induced prompt, substantial, and rapidly reversing increases in the concentrations of these metabolites of adenine nucleotides in plasma. The finding that fructose induced almost-immediate increases in the plasma concentrations of inosine, hypoxanthine, and xanthine is consistent with previous studies in rats, in which parenteral administration of fructose induced almost-immediate decreases of total adenine nucleotides (ATP + ADP + AMP) in the liver, and increased concentrations of uric acid and allantoin in the plasma.
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PMID:Liquid-chromatographic measurements of inosine, hypoxanthine, and xanthine in studies of fructose-induced degradation of adenine nucleotides in humans and rats. 369 69


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