Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ceruloplasmin (CP) was found to inhibit xanthine oxidase and ferritin-dependent peroxidation of phospholipid liposomes, as evidenced by decreased malondialdehyde formation. Ceruloplasmin was also shown to inhibit superoxide-mediated mobilization of iron from ferritin, in a concentration-dependent manner, as measured spectrophotometrically using the iron(II) chelator bathophenanthroline sulfonate. Ceruloplasmin failed to function as a peroxyl radical-scavenging antioxidant as evidenced by its inability to inhibit free radical-initiated peroxidation of linoleic acid, suggesting that CP inhibited lipid peroxidation by affecting the availability of ferritin-derived iron. In addition, CP scavenged xanthine oxidase-derived superoxide as measured spectrophotometrically via its effect on cytochrome c reduction. However, the extent of the superoxide scavenging of CP did not quantitatively account for its effects on iron release, suggesting that CP inhibits superoxide-dependent mobilization of ferritin iron independently of its ability to scavenge superoxide. The effects of CP and apoferritin on iron-catalyzed lipid peroxidation in systems containing exogenously added ferrous iron was also investigated. In the absence of apoferritin, CP exhibited a concentration-dependent prooxidant effect. However, CP-dependent, iron-catalyzed lipid peroxidation was inhibited by the addition of apoferritin. Apoferritin did not function as a peroxyl radical-scavenging antioxidant but was shown to incorporate iron in the presence of CP. These data suggest that CP inhibits superoxide and ferritin-dependent lipid peroxidation largely via its ability to reincorporate reductively mobilized iron back into ferritin.
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PMID:Inhibition of superoxide and ferritin-dependent lipid peroxidation by ceruloplasmin. 253 39

Human colostrum manifests antioxidant properties, being capable of spontaneous reduction of cytochrome c, depletion of polymorphonuclear leukocyte-produced H2O2 and protection of epithelial cells from PMN-mediated detachment. These activities can be electrophoretically concentrated at either 3.5 kD or 50 kD dialysis membranes at mildly alkaline pH. They are progressively lost under increasingly alkaline conditions. They are resistant to 1-mM N-ethylmaleimide. Examination of a series of antioxidant compounds showed that ascorbate manifests several characteristics of colostrum, being able to reduce cytochrome c and deplete H2O2 but not altering PMN-mediated HEp2 cell detachment. Addition of ascorbate oxidase to colostrum decreased its cytochrome c-reducing activity by more than 85%, decreased its H2O2-depleting activity by nearly 50%, but did not alter its ability to protect HEp2 cells, all suggesting heterogeneity of colostral antioxidant activities. Treatment of colostrum with an enzymatic system (xanthine + xanthine oxidase) known to destroy ascorbate's cytochrome c-reducing activity yielded paradoxical results, decreasing colostral cytochrome c reduction in a dose-related manner, while increasing its H2O2-depleting activity. These studies demonstrate that a colostral component similar to ascorbate, a known antioxidant compound is responsible for the majority of colostral cytochrome c-reducing activity, for about half of its H2O2-depleting activity, and little, if any, of its protective effect on HEp2 cells. Thus colostral antioxidant activity is heterogeneous.
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PMID:Further characterization of human colostral antioxidants: identification of an ascorbate-like element as an antioxidant component and demonstration of antioxidant heterogeneity. 253 79

Failure to eradicate mucoid forms of P. aeruginosa has implicated bacterial alginate in a local evasion of host defence mechanisms within the lung of Cystic Fibrosis (CF) patients. We have found that purified bacterial alginate scavenges free radicals released by triggered macrophages as detected by lucigenin amplified chemiluminescence (CL) and reduction of cytochrome c. In agreement with this, alginate was also able to scavenge radicals generated by a chemical system (hydrogen peroxide and copper; detected by benzoate hydroxylation and chemiluminescence), and by an enzymatic system (hypoxanthine and xanthine oxidase; detected by chemiluminescence). All inhibitions were dose-related. Oxygen consumption by neutrophils (unlike that of macrophages) could be detected in a Clark electrode, and was not reduced by alginate, confirming that scavenging of radicals was responsible for the earlier observations. These data suggest that bacterial alginate by scavenging free radicals, may favour the survival of mucoid forms of P. aeruginosa, particularly in the CF lung.
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PMID:Scavenging by alginate of free radicals released by macrophages. 254 67

Novel metal complexes, Fe(II)-tetrakis-N,N,N',N' (2-pyridylmethyl)ethylenediamine(Fe-TPEN) and Fe(III)-tris[N-(2-pyridylmethyl)-2-aminoethyl]amine (Fe-TPAA), catalyzed the dismutation of superoxide, and 0.8 microM Fe-TPEN and 7.5 microM Fe-TPAA were equivalent to 1 unit of superoxide dismutase (SOD) activity in the xanthine oxidase-cytochrome c assay. Addition of serum albumin had no effect on the activities of Fe-TPEN and Fe-TPAA but depressed those of the Cu(salicylate)2 and Cu(diisopropylsalicylate)2 complexes. Both iron complexes blocked the toxic effect of paraquat on Escherichia coli growth and survival without causing induction of SOD. In contrast, this behavior was not seen with other SOD mimics containing copper or manganese. These results support the view that the SOD activities of these iron complexes remain intact in living cells.
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PMID:Superoxide dismutase mimics based on iron in vivo. 254 3

The effects of lentinan on enzyme induced lipid peroxidation, xanthine-xanthine oxidase-induced cytochrome c reduction, and on the superoxide-dismutase (SOD) enzyme activity and expression of human lymphocytes and erythrtocytes were studied. Lentinan in low concentration decreased SOD activity of lymphocytes and erythrocytes from healthy subjects. In higher concentration (10 micrograms/ml) lentinan increased the pathologically low SOD activity of erythrocytes and lymphocytes of patients with cirrhosis of the liver. No significant antioxidant (free radical scavenger) effect has been observed in NADPH-induced and Fe3+-stimulated lipid peroxidation and in xanthine-xanthine oxidase system.
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PMID:Effect of lentinan on superoxide dismutase enzyme activity in vitro. 254 63

In the present work, an experimental system was designed to study superoxide anion radical, implicated as the cause of vascular dilatation. To circumvent its direct effect, we employed a two-bath system. When the endothelial cells (EC) were exposed to electrical field stimulation (EFS) or to a hypoxanthine-xanthine oxidase system in bath A plus its physiological buffer solution suffused on a helical strip of cat basilar artery in bath B, the contraction to 5-hydroxytryptamine (5-HT) was depressed to approximately 40-50% of the control value. The reduction was not elicited on EFS in a state of calcium deficiency or in the absence of EC. The depression could be prevented by pretreatment with superoxide dismutase (SOD), but not with an effective dose of catalase, dimethyl sulfoxide (DMSO), mannitol, or indomethacin. The percent depression of contraction was paralleled by an increase in SOD-inhibitable cytochrome c reduction, which was not associated with cyclic guanosine 3',5'-monophosphate formation. These results suggest that superoxide-dependent relaxing factor is released from EC differently than the endothelium-derived relaxing factor mediated by acetylcholine.
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PMID:Release of superoxide-dependent relaxing factor(s) from endothelial cells. 255 45

Impairment of lysosomal stability due to reactive oxygen species generated during the oxidation of hypoxanthine by xanthine oxidase was studied in rat liver lysosomes isolated in a discontinuous Nycodenz gradient. Production of O2.- and H2O2 during the hypoxanthine/xanthine oxidase reaction occurred for at least 5 min, while lysosomal damage, indicated by the release of N-acetyl-beta-glucosaminidase, occurred within 30 s, there being no further damage to these organelles thereafter. The extent of lysosomal enzyme release increased with increasing xanthine oxidase concentration. Superoxide dismutase and catalase did not prevent lysosomal damage during the hypoxanthine/xanthine oxidase reaction. Lysosomes reduced xanthine oxidase activity, as assessed in terms of O2 consumption, only slightly but substantially inhibited in a competitive manner the O2.- -mediated reduction of cytochrome c. This inhibition was almost completely reversed by potassium cyanide, thus pointing to the presence of a cyanide-sensitive superoxide dismutase in the lysosomal fraction. However, potassium cyanide did not affect the hypoxanthine/xanthine oxidase-mediated lysosomal damage, thus suggesting an inability of the lysosomal superoxide dismutase to protect the organelles. Negligible malondialdehyde formation was observed in the lysosomes either during the hypoxanthine/xanthine oxidase reaction or with different selective experimental approaches known to produce lipid peroxidation in other organelles such as microsomes and mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lysosomal enzyme leakage during the hypoxanthine/xanthine oxidase reaction. 256 86

Trimetazidine at concentrations above 100 microM competed with cytochrome c in scavenging O2.- radicals formed by the reaction catalyzed by the xanthine oxidase enzyme upon xanthine. This scavenger effect was also observed when O2.- were generated by active human neutrophils in which the rate of O2.- formation was monitored by following the reduction of cytochrome c or the emission of luminol-dependent chemiluminescence. An additional scavenger effect of trimetazidine was measured in a OH. chemical generating system whereby the breakdown of deoxyribose by the thiobarbituric acid assay was detected. This study suggests that trimetazidine might function as an antioxy radical compound in conditions of increased oxy radical production.
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PMID:Anti oxy-radical properties of trimetazidine. 274 Jun 16

Phenol and 1-naphthol, products of benzene and naphthalene biotransformation, are metabolized during O2- generation by xanthine oxidase/hypoxanthine and phorbol myristate acetate (PMA)-stimulated human neutrophils. The addition of 1-naphthol to xanthine oxidase/hypoxanthine incubations resulted in the formation of 1,4-naphthoquinone (1,4-NQ) whereas phenol addition yielded only small quantities of hydroquinone, catechol and a unidentified reducible product but not 1,4-benzoquinone. This formation of 1,4-NQ was dependent upon hypoxanthine, xanthine oxidase, and 1-naphthol and was inhibited by the addition of superoxide dismutase (SOD) demonstrating that the conversion was O2-mediated. During O2- generation by PMA-stimulated neutrophils, the addition of phenol interfered with luminol-dependent chemiluminescence and resulted in covalent binding of phenol to protein. Protein binding was 80% inhibited by the addition of azide or catalase to the incubations indicating that bioactivation was peroxidase-mediated. In contrast, the addition of 1-naphthol to PMA-stimulated neutrophils interfered with superoxide-dependent cytochrome c reduction as well as luminol-dependent chemiluminescence and also resulted in protein binding. Protein binding was only partially inhibited by azide or catalase. The addition of SOD in combination with catalase resulted in a significantly greater inhibition of binding when compared to that of catalase alone. The results of these experiments indicate that phenol and 1-naphthol are converted to reactive metabolites during superoxide generating conditions but by different mechanisms. The formation of reactive metabolites from phenol was almost exclusively peroxidase-mediated whereas the bioactivation of 1-naphthol could occur by two different mechanisms, a peroxidase-dependent and a direct superoxide-dependent mechanism.
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PMID:Metabolic activation of 1-naphthol and phenol by a simple superoxide-generating system and human leukocytes. 282 May 96

MnO2 reacted with desferrioxamine B yielding a green, water-soluble complex, with absorption maxima at 315 and 635 nm whose extinction coefficients were 925 and 60 M-1 cm-1, respectively. Increasing the proportion of ligand to metal increased both color yield and ability to scavenge O2-, with maximal color yield and activity being achieved at a 1:1 ratio. The complex catalyzed the dismutation of O2- and 1 microM was equivalent to 1 unit of superoxide dismutase activity in the xanthine oxidase-cytochrome c assay. The complex thus exhibited approximately 0.1% as much activity as did the manganese-containing superoxide dismutase, on the basis of manganese content. The activity of the complex was not suppressed by bovine serum albumin or by the soluble proteins extracted from Lactobacillus plantarum. In contrast, the activities of Cu(II) complexes of salicylate or Gly-His-Lys were suppressed by these proteins.
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PMID:A mimic of superoxide dismutase activity based upon desferrioxamine B and manganese(IV). 282 13


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