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)

The ability of Oxyphenbutazone (a non-steroidal antiinflammatory drug) to react with singlet oxygen and superoxide anions, possible mediators of the damage to the lipids of the cell membranes during inflammation was studied. Oxyphenbutazone inhibited the reduction of nitroblue tetrazolium in aerobic riboflavin-photosensitized oxidation of methionine, but did not influence the cytochrome C-reduction by superoxide-generating system xanthine-xanthine oxidase. Oxyphenbutazone was photooxidized in the presence of Rose Bengal, the latter being a photosensitizer. The increase of the reaction rate of Oxyphenbutazone-oxidation in D2O as compared to H2O, as well as the inhibition of oxidation by singlet oxygen-quencher sodium azide confirmed the participation of singlet oxygen in this process. It was found that Oxyphenbutazone reacted with singlet oxygen, but did not react with superoxide anions. This was supported by the observed protection of erythrocyte membranes from the hemolytic action of the singlet oxygen-generating system Rose Bengal + light.
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PMID:Reactions of oxyphenbutazone with active oxygen species. 282 29

D.c. polarography of 2-amino-6-chloropurine in aqueous medium over a broad pH range revealed two diffusion waves, the first of which corresponds to reduction of the C(6)-Cl bond, leading to formation of 2-aminopurine in high yield. Condensation of the sodium salt of 2-aminopurine with (2-acetoxyethoxy)methyl chloride led to the two isomeric 9- and 7-(2-hydroxyethoxymethyl)-2-aminopurines. The 9- isomer, 6-deoxyacyclovir, a prodrug of acyclovir previously synthesized by another route, was readily converted to the latter by xanthine oxidase; the 7-isomer was not a substrate. The intense fluorescence of 6-deoxyacyclovir makes it a convenient fluorescent substrate for xanthine oxidase, although less sensitive than xanthine; it is shown that 2-aminopurine would be a very sensitive fluorescent substrate. The polarographic behaviour of the riboside of 2-amino-6-chloropurine was virtually identical with that of the parent purine, leading to a simple procedure for conversion of 2-amino-6-chloropurine nucleosides and acyclonucleosides to the corresponding 2-aminopurine congeners.
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PMID:Preparative electrochemical reduction of 2-amino-6-chloropurine and synthesis of 6-deoxyacyclovir, a fluorescent substrate of xanthine oxidase and a prodrug of acyclovir. 283 54

The specific thiol protease inhibitor, NCO-700, which is related to L-trans-epoxysuccinylpeptides, inhibited oxidant production by chemoattractant-stimulated rabbit polymorphonuclear leukocytes. NCO-700 could also scavenge active oxygen generated from sodium hypochlorite-hydrogen peroxide and hypoxanthine-xanthine oxidase systems.
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PMID:Effect of NCO-700, an inhibitor of thiol protease, on reactive oxygen production by chemotactic peptide-stimulated rabbit peripheral granulocytes. 283 17

The detergent-induced amplification of lucigenin-dependent chemiluminescence of O2-, generated by xanthine oxidase or microsomal NADPH oxidase was studied. An assay system is described which is at least 10 times more sensitive than normal lucigenin-dependent chemiluminescence due to the amplification by high concentrations of octylphenylpolyethylene glycol (Triton X-100). Compared to the superoxide dismutase-sensitive reduction of acetylated cytochrome c, a 3750-fold lower amount of microsomal protein was necessary to produce an O2- signal 10-fold above the background. In contrast to cytochrome c reduction, detergent-amplified chemiluminescence of lucigenin was completely inhibited by superoxide dismutase and therefore more selective for O2-. The membrane-bound and Triton X-100-solubilized NADPH oxidase from microsomes of macrophages was activated by ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid and inhibited by Ca2+ and sodium dodecyl sulfate. The membrane-bound enzyme showed a Km value of 1.35 microM, which decreased to 0.95 microM after the addition of 12% (g/g) Triton X-100. The Km and Vmax values of soluble xanthine oxidase were not influenced by Triton X-100, indicating that the enzyme activities were not impaired by the high concentrations of detergent.
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PMID:Detergent-amplified chemiluminescence of lucigenin for determination of superoxide anion production by NADPH oxidase and xanthine oxidase. 283 20

The effect of superoxide radical on the azide-insensitive ATP-dependent Ca2+-transport by a plasma membrane (PM)-enriched fraction (F2) and an endoplasmic reticulum (ER)-enriched fraction (F3) isolated from pig coronary artery was examined using xanthine oxidase plus xanthine to generate superoxide ions. A preincubation with xanthine oxidase plus xanthine at 37 degrees C preferentially inactivated the oxalate-stimulated Ca2+ uptake by the F3 fraction rather than the phosphate-stimulated uptake by the F2 fraction, indicating that the Ca2+ pump in the ER was more susceptible to this free radical. The inactivation of the Ca2+ uptake depended on the concentrations of xanthine oxidase and xanthine in the preincubation mixture as well as on the preincubation time. Furthermore, the inclusion of superoxide dismutase in the preincubation mixture prevented the inactivation. Thus the inactivation was caused by superoxide radical. Preincubation with xanthine oxidase plus xanthine, however, altered the half-life of efflux of Ca2+ from these vesicles only marginally. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the F3 fraction showed formation of a Ca2+-dependent acid stable phosphoenzyme at 0 degree C predominantly at a protein band corresponding to 100 kDa. The level of the 100-kDa acylphosphate intermediate was inhibited in parallel with the inhibition of the Ca2+ uptake by preincubation with xanthine oxidase plus xanthine. We conclude that superoxide radical inactivates the ER Ca2+ transport by lowering the level of the phosphoenzyme.
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PMID:Effect of superoxide radical on Ca2+ pumps of coronary artery. 284 93

The protective effects of various tannins on ocular lens against the induced oxidative damage were examined. Oxidative damage on mouse lenses was induced by incubating them with xanthine-xanthine oxidase, ADP and Fe3+ (X.XOD system). X.XOD system caused an increase in lipid peroxide of lens membrane and decreases in Na,K-ATPase and GSH reductase activities in the lenses. After pretreatment of lenses with X.XOD system, the lenses were incubated with tannins in the medium containing no X.XOD system and the effects of tannins on biochemical parameters in the lenses were determined. Higher molecular tannins (penta-O-galloyl-beta-D-glucopyranose and geraniin) decreased the lipid peroxide in the lens and restored GSH content, Na,K-ATPase and GSH reductase activities in the lens to the level comparable to control. However, all of tannins tested restored much insufficiently the cation level (ratio of Na+/K+) in the lens regardless of extents of restoration of Na,K-ATPase level by them. Because it was supposed that tannins might act primarily on the plasma membrane, the effect of tannins on lens plasma membrane was examined using cell free system. Lens was homogenated and separated into membrane pellet and supernatant. When the pellet was treated with X.XOD system, the lipid peroxide in the pellet increased and its Na,K-ATPase activity decreased. In addition, the treated pellet decreased the GSH level and GSH reductase activity in the supernatant, when the pellet was combined with the supernatant. Higher molecular tannins reduced lipid peroxide content in the X.XOD-treated pellet to control level and the pellet in which lipid peroxide content was reduced by tannins caused much less decreases of GSH level and GSH reductase activity in the supernatant. These results suggest that, in intact lens, higher molecular tannins act on plasma membrane to eliminate lipid peroxide produced by the X.XOD system and consequently suppress the decreases in both Na,K-ATPase and GSH reductase activities without their entering inside the cell.
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PMID:Effects of tannins on the oxidative damage of mouse ocular lens. I. Using the oxidative damage model induced by the xanthine-xanthine oxidase system. 284 23

The generation of superoxide radicals from xanthine oxidase-hypoxanthine in a particulate fraction of gerbil cerebral cortex influenced the activity of the synaptic enzyme adenylate cyclase, as well as Mn2+- and Na+,K+-sensitive forms of ATPase. Low concentrations of xanthine oxidase actually elevated the sensitivity of adenylate cyclase to GTP, GTP + norepinephrine (NE), and forskolin but not significantly to Mn2+. Higher levels of xanthine oxidase elicited a marked inhibition of these responses. The stimulation of adenylate cyclase mechanisms requiring GTP (GTP, forskolin, and NE) was more susceptible than was Mn2+, suggesting that the guanine nucleotide stimulatory protein was more vulnerable to free radical attack than the catalytic site of adenylate cyclase. Superoxide dismutase (SOD), but not catalase, partially protected the forskolin-sensitive enzyme from the action of xanthine oxidase-hypoxanthine. A combination of SOD plus catalase preserved enzyme responses to forskolin. In comparison, additions of SOD plus mannitol or catalase plus flunarizine were less effective. The sensitivity of the particulate ATPase to Mn2+ was more labile to the consequence of superoxide formation than Na+, K+ -ATPase. In this regard the Ca2+,Mg2+ sensitivity of the enzyme was reduced only to a marginal extent. The findings might be analogous to in vivo data in which cerebral adenylate cyclase and Na+, K+-ATPase are damaged following postischemic reperfusion in gerbils, a process thought to be mediated by free radicals.
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PMID:Free radicals generated by xanthine oxidase-hypoxanthine damage adenylate cyclase and ATPase in gerbil cerebral cortex. 285 Apr 58

In this study we prepared sarcolemmal fractions from bovine and rat hearts; their Na+K+ ATPase activities, measured in the presence of saponin to unmask latent Na+K+ ATPase, were 59.4 and 48.8 mu mol Pi/mg protein.h, respectively. The rate of Na+ dependent Ca2+ uptake was linear for the first 10 s and a plateau was reached in 3 min. Oxidation by free radical generation either with H2O2, FeSO4 plus DTT or xanthine oxidase plus hypoxanthine stimulated Na+/Ca2+ exchange in a time-dependent manner. The stimulation was abolished by deferoxamine or o-phenanthroline. By contrast, oxidation by HOCl inhibited Na+/Ca2+ exchange in proportion to its concentration, and this inhibition was antagonized by DTT. DTT alone had no effect on the exchange. Insulin stimulated Na+/Ca2+ exchange, its maximal effect was attained after 30 min incubation with 100 mu units/ml. N-ethylmaleimide inhibited the exchange both in the presence and in the absence of insulin. Sarcolemmal fractions prepared from hearts of alloxan-treated, acutely diabetic rats showed a significant decrease in Na+/Ca2+ exchange. Addition of insulin in vitro significantly stimulated Na+/Ca2+ exchange of both diabetic and control groups. The results indicate that sarcolemmal Na+/Ca2+ exchange function is modulated by oxidation-reduction states and by the presence of insulin.
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PMID:Na+/Ca2+ exchange of isolated sarcolemmal membrane: effects of insulin, oxidants and insulin deficiency. 285 14

Sulfasalazine suppresses mucosal injury in patients with ulcerative colitis, but the mechanism of its therapeutic action is uncertain. In the present study, we examined the mechanism of the protective action of sulfasalazine in a rat model in which colonic epithelial cell loss and subsequent increases in epithelial proliferative activity were induced by intracolonic instillation of sodium deoxycholate. Sulfasalazine or its therapeutically active metabolite 5-aminosalicylic acid suppressed the loss of deoxyribonucleic acid into the colonic lumen and the subsequent increases in mucosal ornithine decarboxylase activity and tritiated thymidine incorporation into deoxyribonucleic acid induced by sodium deoxycholate. Sulfasalazine and 5-aminosalicylic acid also blocked xanthine-xanthine oxidase-induced loss of deoxyribonucleic acid and the subsequent proliferative response. In vitro sodium deoxycholate increased reactive oxygen formation by colonic mucosal scrapings or isolated crypt epithelium. These actions of sodium deoxycholate on reactive oxygen formation were blocked by sulfasalazine or 5-aminosalicylic acid. Sulfapyridine, a therapeutically inactive metabolite of sulfasalazine, had no effect on sodium deoxycholate-induced increases in surface cell sloughing, ornithine decarboxylase, tritiated thymidine incorporation into deoxyribonucleic acid, chemiluminescence, or superoxide production. The ability of sulfasalazine and 5-aminosalicylic acid to scavenge reactive oxygen may play a role in their therapeutic effects of inflammatory bowel disease.
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PMID:Actions of sulfasalazine and 5-aminosalicylic acid as reactive oxygen scavengers in the suppression of bile acid-induced increases in colonic epithelial cell loss and proliferative activity. 288 67

Preincubation of rat brain synaptosomes with xanthine and xanthine oxidase (X/XO) in Ca2+-free Krebs buffer resulted in a 27% inhibition of synaptosomal gamma-aminobutyric acid (GABA) uptake. Addition of 1.5 mM CaCl2 increased the inhibition with X/XO to 46%, and inhibition was essentially complete when the calcium ionophore A23187 also was included. In other studies, preincubation of purified rat brain mitochondria with the combination of X/XO and 4 microM CaCl2 produced a significant (38%) decrease in state 3 respiration with glutamate/malate as substrate that was not seen with either X/XO or Ca2+ alone. Similar results were obtained using cultured mouse spinal cord neurons in which incubation with X/XO/ADP/FeCl2 and A23187 produced membrane damage as assessed by a 32% reduction of neuronal Na+, K+-ATPase activity. Neither X/XO/ADP/FeCl2 nor A23187 alone caused detectable inhibition. These results demonstrate the synergistic damaging effect of free radicals and Ca2+ on membrane function. In addition, they suggest that free radical-induced peroxidation of membrane lipid, occurring focally during complete or nearly complete ischemia in vivo, could result in intense cellular perturbation when coupled with increased intracellular Ca2+.
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PMID:Calcium enhances in vitro free radical-induced damage to brain synaptosomes, mitochondria, and cultured spinal cord neurons. 299 23


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