Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Metallothionein inhibited in a concentration-dependent fashion the reduction of nitroblue tetrazolium [NBT] mediated by xanthine oxidase and by NADH-phenazine methosulfate. This catalytic activity of metallothionein for dismutation of O2- is dependent on the copper content in metallothionein.
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PMID:Inhibition of nitroblue tetrazolium reduction by metallothionein. 689 6

Superoxide radicals were investigated as to their capability of depolymerizing the hyaluronic acid of the bovine vitreous body. Using viscometry it was found that O2 radicals, generated by the hypoxanthine/xanthine oxidase method or the combination of NADH and phenazine methosulphate, degraded hyaluronic acid. This reaction was suppressed by superoxide dismutase, catalase, and peroxidase. In contrast, the depolymerization of hyaluronic acid by oxidation-reduction systems like ascorbic acid or ferrous ions was abolished by catalase and peroxidase while superoxide dismutase showed no effect.
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PMID:The inability of superoxide dismutase to inhibit the depolymerization of hyaluronic acid by ferrous ions and ascorbate. 690 74

Aconitase is a member of a family of iron-sulfur-containing (de)hydratases whose activities are modulated in bacteria by superoxide radical (O2-.)-mediated inactivation and iron-dependent reactivation. The inactivation-reactivation of aconitase(s) in cultured mammalian cells was explored since these reactions may impact important and diverse aconitase functions in the cytoplasm and mitochondria. Conditions which increase O2-. production including exposure to the redox-cycling agent phenazine methosulfate (PMS), inhibitors of mitochondrial ubiquinol-cytochrome c oxidoreductase, or hyperoxia inactivated aconitase in mammalian cells. Overproduction of mitochondrial Mn-superoxide dismutase protected aconitase from inactivation by PMS or inhibitors of ubiquinol-cytochrome c oxidoreductase, but not from normobaric hyperoxia. Aconitase activity was reactivated (t1/2 of 12 +/- 3 min) upon removal of PMS. The iron chelator deferoxamine impaired reactivation and increased net inactivation of aconitase by O2-.. The ability of ubiquinol-cytochrome c oxidoreductase-generated O2-. to inactivate aconitase in several cell types correlated with the fraction of the aconitase activity localized in mitochondria. Extracellular O2-. generated with xanthine oxidase did not affect aconitase activity nor did exogenous superoxide dismutase decrease aconitase inactivation by PMS. The results demonstrate a dynamic and cyclical O2-.-mediated inactivation and iron-dependent reactivation of the mammalian [4Fe-4S] aconitases under normal and stress conditions and provide further evidence for the membrane compartmentalization of O2-..
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PMID:Superoxide radical and iron modulate aconitase activity in mammalian cells. 776 42

We have shown previously that human neutrophil microsomes contain a highly specific dehydrogenase which, in the presence of NADP+, converts 5S-hydroxy-6,8,11,14-eicosatetraenoic acid (5S-HETE) to its 5-oxo metabolite, 5-oxo-ETE, a potent agonist of these cells. However, intact neutrophils convert 5S-HETE principally to its omega-oxidation product, 5,20-diHETE, and to only small amounts of 5-oxo-ETE. Phorbol myristate acetate (PMA) dramatically shifts the metabolism of 5S-HETE by intact cells so that 5-oxo-ETE is the major metabolite. The objective of this investigation was to determine the mechanism for the stimulatory effect of PMA on 5-oxo-ETE formation. The possibility that oxidants released in response to PMA nonenzymatically oxidized 5S-HETE was ruled out, since PMA did not appreciably stimulate the formation of 5-oxo-ETE from 5R-HETE. On the other hand, inhibition of NADPH oxidase either by diphenylene iodonium or by mild heating nearly completely prevented the stimulatory effect of PMA on the formation of 5-oxo-ETE. The possibility that this effect was mediated by superoxide seems unlikely, since it was still observed, although somewhat attenuated, in the presence of superoxide dismutase. Moreover, superoxide generated by another mechanism (xanthine/xanthine oxidase) did not appreciably affect the formation of 5-oxo-ETE by neutrophils. However, phenazine methosulfate, which can nonenzymatically convert NADPH to NADP+, mimicked the effect of PMA on 5-oxo-ETE formation by intact neutrophils. It is concluded that PMA acts by activating NADPH oxidase, resulting in conversion of NADPH to NADP+, which enhances the formation of 5-oxo-ETE and reduces the formation of 5,20-diHETE. Serum-treated zymosan has an effect on the metabolism of 5S-HETE similar to that of PMA in that it also stimulates the formation of 5-oxo-ETE and inhibits that of 5,20-diHETE.
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PMID:Phorbol myristate acetate stimulates the formation of 5-oxo-6,8,11,14-eicosatetraenoic acid by human neutrophils by activating NADPH oxidase. 792 34

Our laboratory recently isolated free PQQ (2,7,9-tricarboxy-pyrroloquinoline quinone, methoxatin), a bacterial redox cofactor, from red cells, neutrophils, serum and milk and found free PQQ in CSF, synovial fluid and bile. The metabolism and functions of PQQ and ascorbate may be coupled. Physiologically, free PQQ catalyzes dioxygen-superoxide interconversion, and participates in both superoxide generation (respiratory burst) and scavenging (cell protection). Using a labeled aromatic o-diamine, superoxide formation by activated neutrophils was inhibited and the labeled phenazine adduct of PQQ could be isolated from the inhibited cells (Karnovsky et al., 1992). PQQ may convert xanthine oxidase to xanthine dehydrogenase (XD) and could be the physiological coenzyme of XD. PQQ plus copper, form a potent amine-oxidizing system. Shah et al., 1992 found that PQQ-Cu2+ catalyzes the oxidation of epsilon-amino groups in collagen and elastin. Rucker's lab (Smidt et al., 1991) has found that PQQ may be a vitamin for mouse pups. Watanabe et al., 1988 and Nishigori et al., 1989, showed that injected PQQ protects animals against oxidative stress injury. PQQ's in vivo antioxidant action, spares reduced glutathione. PQQ, as an actively transported organic anion, concentrates in cells. In other experiments (Aizenman et al., 1992), PQQ protected neurons against the neurotoxin action of the glutamate-receptor against NMDA. We shall consider possible roles for PQQ in the biosynthesis of nitric oxide (NO, endothelium-derived relaxing factor, EDRF) from L-arginine and in NO removal by superoxide. NO has now been linked to the inhibition of osteoclastic bone resorption.
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PMID:Is the antioxidant, anti-inflammatory putative new vitamin, PQQ, involved with nitric oxide in bone metabolism? 840 96

The airways of cystic fibrosis patients colonised by Pseudomonas aeruginosa contain the redox active phenazine derivative, 1-hydroxyphenazine (OHP). As the presence of reactive oxygen species is of importance to tissue damage in cystic fibrosis, OHP was investigated for its ability to reduce molecular oxygen to superoxide. In the presence of NADPH, OHP reduced cytochrome c in a dose-dependent manner. This effect was not inhibited by superoxide dismutase and demonstrates an electron transport role for OHP. The OHP/NADPH system was unable to reduce molecular oxygen to superoxide as judged by an inability to oxidase epinephrine to adrenochrome. However, using lucigenin-enhanced chemiluminescence to detect superoxide, it was found that pathophysiologically relevant concentrations of OHP (5-25 microM) effectively scavenged superoxide from a xanthine/xanthine oxidase system. Similarly, in the presence of OHP, superoxide availability from contact-activated neutrophils was substantially reduced. It is concluded that OHP is an efficient scavenger of superoxide and that electron transfer from superoxide to OHP represents a major mechanism for reduction of OHP in vivo. Reduced OHP has the potential to alter cellular function by participating in the reduction of iron-containing proteins and in this manner contribute to the pathogenesis of P. aeruginosa infection in cystic fibrosis.
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PMID:Scavenging of neutrophil-derived superoxide anion by 1-hydroxyphenazine, a phenazine derivative associated with chronic Pseudomonas aeruginosa infection: relevance to cystic fibrosis. 854 51

The effect of eugenol on xanthine oxidase (XO) xanthine(X)-Fe+3-ADP mediated lipid peroxidation was studied in liver microsomal lipid liposomes. Eugenol inhibited the lipid peroxidation in a dose dependent manner as assessed by formation of thiobarbituric acid reactive substances. When tested for its effect on XO activity per se, (by measuring uric acid formation) eugenol inhibited the enzyme to an extent of 85% at 10 microm concentration and hence formation of O2.- also. However, the concentration of eugenol required for XO inhibition was more in presence of metal chelators such as EDTA, EGTA and DETAPAC, but not in presence of deferoxamine, ADP and citrate. The antiperoxidative effect of eugenol was about 35 times more and inhibition of XO was about 5 times higher as compared to the effect of allopurinol. Eugenol did not scavenge O2.- generated by phenazine methosulfate and NAD but inhibited propagation of peroxidation catalyzed by Fe2+ EDTA and lipid hydroperoxide containing liposomes. Eugenol inhibits XO-X-Fe+3 ADP mediated peroxidation by inhibiting the XO activity per se in addition to quenching various radical species.
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PMID:Inhibition of xanthine oxidase-xanthine-iron mediated lipid peroxidation by eugenol in liposomes. 904 22

The human red blood cell (RBC) is known to be susceptible to oxidant damage, with both structural and functional properties altered consequent to oxidant attack. Such oxidant-related alterations may lead to changes of RBC rheologic behavior (i.e., deformability, aggregability). Two different models of oxidant stress were used in this study to generate superoxide anions either internal or external to the RBC. Our results indicate that generation of superoxide within the RBC by phenazine methosulfate decreases RBC deformability without effects on cell aggregation. Conversely, superoxide generated externally by the xanthine oxidase-hypoxanthine system primarily affects RBC aggregability: the shear rate necessary to disaggregate RBC was markedly increased while the extent of aggregation decreased slightly. Increased disaggregation shear rate (i.e., greater aggregate strength) as a result of superoxide radical damage may adversely affect the dynamics of blood flow in low-shear portions of the circulation, and may also play a role in the no-reflow phenomena encountered after ischemia-reperfusion.
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PMID:Effect of superoxide anions on red blood cell rheologic properties. 943 19

Lignin is one of the major components of dietary fiber. It is a complex hydrophobic molecule that typically occurs in cell walls with heteroxylans. Our experimental data show that lignin is a free radical scavenger. When the NADH-phenazine methosulfate-nitro blue tetrazolium free radical-producing system is used, an alkali-lignin concentration of 46.29 micrograms/ml that causes 50% inhibition of uric acid production by xanthine oxidase (IC50) is a scavenger of superoxide anion radicals. Spectrophotometric assay has shown that alkali-lignin with an IC50 of 59.08 micrograms/ml inhibits the activity of xanthine oxidase, one of the enzymes related to the production of superoxide anion radicals, and presents a mixed-type noncompetitive inhibition pattern. Using the deoxyribose method, we have found that alkali-lignin is a hydroxyl radical scavenger with an IC50 of 250 micrograms/ml, and using the thiobarbituric acid method, we can see that alkali-lignin inhibits nonenzymatic and enzymatic lipid peroxidation with an IC50 of 72 and 100 micrograms/ml, respectively. Alkali-lignin also hinders the activity of glucose-6-phosphate dehydrogenase, another enzyme related to the generation of superoxide anion radicals, with an IC50 of 123.6 micrograms/ml, and obstructs the growth and viability of cancer (HeLa) cells in a dose-dependent manner. Our experimental results suggest another mechanism whereby the free radical-scavenging activity of lignin in dietary fiber may be involved in the fiber-colon cancer interaction. We also suggest that the ability of dietary fiber to protect against colon cancer may be partly determined by the amount of lignin in dietary fiber as well as the free radical-scavenging ability of lignin.
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PMID:Free radical-scavenging properties of lignin. 950 10

Calcium dobesilate possesses antioxidant properties in vitro, but the in vivo significance and putative angioprotective role of these properties are undefined. Here, calcium dobesilate was tested in a newly developed in vivo model of microvascular permeabilization induced by reactive oxygen species in the rat peritoneal cavity. In this model, microvascular permeabilization is equated to the rate of Evans blue extravasation toward the peritoneal cavity. Basal Evans blue extravasation (rate constant values ke = 0.0176 +/- 0.0015 h-1) was markedly and significantly increased by reactive oxygen species generated in situ, with: (i) phenazine methosulfate/NADH (delta ke(phenazine methosulfate) = 0.0419 +/- 0.0043 h-1) and (ii) xanthine/xanthine oxidase (delta ke(xo) = 0.0383 +/- 0.0010x h-1). These actions of reactive oxygen species were abolished by locally injected superoxide dismutase (i.p., 300 units/kg). Intraperitoneally given calcium dobesilate (100 mg/kg) inhibited 75-100% of reactive oxygen species-induced Evans blue extravasation. By the intravenous route, calcium dobesilate i.v. (1-50 mg/kg) dose dependently inhibited phenazine methosulfate-induced Evans blue extravasation with an ID50 of 2-5 mg/kg (full inhibition was reached at 20-50 mg/kg). After single oral administration, calcium dobesilate (5-500 mg/kg) dose dependently inhibited phenazine methosulfate-dependent Evans blue extravasation with an ID50 of 50-100 mg/kg (81% inhibition at 500 mg/kg, P < 0.003). After 7 days of oral calcium dobesilate (50 mg/kg once/day) phenazine methosulfate-induced Evans blue peritoneal extravasation was significantly reduced by half. These effects of calcium dobesilate were similar to those observed with a comparative antioxidant molecule, rutin. In conclusion, rat peritoneal microvascular permeability was strongly increased by reactive oxygen species, an effect that was significantly reduced by intraperitoneal, intravenous and oral calcium dobesilate. These results support the hypothesis that the antioxidant properties of calcium dobesilate could play a role in its angioprotective properties in vivo.
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PMID:Angioprotective action of calcium dobesilate against reactive oxygen species-induced capillary permeability in the rat. 982 87


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