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)

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

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

A previously unidentified fraction lacking xanthine:O2 activity has been isolated during affinity chromatography of bovine milk xanthine oxidase preparations on Sepharose 4B/folate gel. Unlike active, desulfo, or demolybdo forms of xanthine oxidase, this form, which typically comprises about 5% of an unfractionated enzyme solution, passes through the affinity column without binding to it, and is thus easily separated from the other species. The absorption spectrum of this fraction is very similar to that of the active form, but has a 7% lower extinction at 450 nm. Analysis of the fraction has shown that it is a dimer of normal size, but that it does not contain molybdenum or molybdopterin (MPT). The "MPT-free" xanthine oxidase contains 90-96% of the Fe found in active xanthine oxidase, and 100% of the expected sulfide. EPR and absorption difference spectroscopy indicate that the MPT-free fraction is missing approximately half of its Fe/S I centers. The presence of a new EPR signal suggests that an altered Fe/S center may account for the nearly normal Fe and sulfide content. Microwave power saturation parameters for the Fe/S II and Fe/S I centers in the MPT-free fraction are normal, with P1/2 equal to 1000 and 60 mW, respectively. The new EPR signal shows intermediate saturation behavior with a P1/2 = 200 mW. The circular dichroism spectrum of the MPT-free fraction shows distinct differences from that of active enzyme. The NADH:methylene blue activity of the MPT-free fraction is the same as that of active xanthine oxidase which exhibits xanthine:O2 activity, but NADH:cytochrome c and NADH:DCIP activities are diminished by 54 and 37%, respectively.
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PMID:A molybdopterin-free form of xanthine oxidase. 282 75

In a recent publication [(1987) FEBS Lett. 210, 195-198] the authors claim the use of cytochrome c to detect superoxide anion underestimates the real rate of superoxide anion formation on the basis that: (i) the rate of uric acid formation by xanthine oxidase is about 4-fold faster than the rate of cytochrome c reduction and (ii) hydrogen peroxide formed upon dismutation of the superoxide anion generated by xanthine oxidase is capable of reoxidizing ferrocytochrome c. That paper may have been misleading for readers not very familiar with the field of oxygen radicals, since both assumptions are, in fact, incorrect. In this report we demonstrate that the build up in concentration of H2O2 during most reactions in which superoxide anion is being produced is not enough to affect the rate of cytochrome c reduction. Our results suggest that the authors may have been misled by an artifact due to exposure of the samples containing H2O2 to UV light, which generates hydroxyl radicals by photolysis.
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PMID:How relevant is the reoxidation of ferrocytochrome c by hydrogen peroxide when determining superoxide anion production? 282 12


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