Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of lipid peroxidation on the Mg2(+)-independent and Mg2(+)-dependent activity of brain cell membrane 5'-nucleotidase was determined and the affinity of the active sites of Mg2(+)-dependent enzyme for 5'-AMP (substrate) and Mg2+ (activator) was examined. Brain cell membranes were peroxidized at 37 degrees C in the presence of 100 microM ascorbate and 25 microM FeCl2 (resultant) for 10 min. The activity of 5'-nucleotidase and lipid peroxidation products (thiobarbituric acid reactive substances) were determined. At 10 min, the level of lipid peroxidation products increased from 0.20 +/- 0.10 to 17.5 +/- 1.5 nmoles malonaldehyde/mg membrane protein. The activity of Mg2(+)-independent 5'-nucleotidase increased from 0.201 +/- 0.020 in controls to 0.305 +/- 0.028 mumol Pi/mg protein/hr in peroxidized membranes. In the presence of 10 mM Mg2+, the activity increased by 5.8-fold in the peroxidized membrane preparation in comparison to 14-fold in control. In peroxidized preparation, the affinity of active site of Mg2(+)-dependent 5'-nucleotidase for 5'-AMP tripled, as indicated by a significant decrease in Km (Km = 95 +/- 2 microM AMP for control; Km = 32 +/- 2 microM AMP for peroxidized). Vmax was significantly reduced from 3.35 +/- 0.16 in control to 1.70 +/- 0.9 mumoles Pi/mg protein in peroxidized membranes. The affinity of the active site for Mg2+ significantly increased (Km = 6.17 +/- 0.37 mM Mg2+ for control; Km = 4.0 +/- 0.31 peroxidized).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lipid peroxidation as the mechanism of modification of brain 5'-nucleotidase activity in vitro. 236 28

We evaluated the erythrocytes of two patients with hereditary pyrimidine 5'-nucleotidase deficiency. Significant findings included an increased reduced glutathione content, increased incubated Heinz body formation, a positive ascorbate cyanide test, and decreased intraerythrocytic pH. The pentose phosphate shunt activity of the patients' red cells as measured by the release of 14CO2 from 14C-1-glucose was decreased compared to high reticulocyte controls. Glucose-6-phosphate dehydrogenase (G6PD) activity in hemolysates from control erythrocytes was inhibited 43% by 5.5 mM cytidine 5'-triphosphate (CTP) and 50% by 5.5 mM in uridine 5'-triphosphate (UTP) at pH 7.1. CTP was a competitive inhibitor for G6P (Ki = 1.7 mM) and a noncompetitive inhibitor for NADP+ (Ki = 7.8 mM). Glutathione peroxidase, glutathione reductase, and 6-phosphogluconate dehydrogenase were not affected by these compounds. Pentose phosphate shunt activity in control red cell hemolysate at pH 7.1 was inhibited to a similar degree by 5.5 mM CTP or UTP. Since the intracellular concentrations of G6P and NADP+ are below their KmS for G6PD, these data suggest that high concentrations of pyrimidine 5'-nucleotides depress pentose phosphate shunt activity in pyrimidin 5'-nucleotidase deficiency. Thus, this impairment of the pentose phosphate pathway appears to contribute to the pathogenesis of hemolysis in pyrimidine 5'-nucleotidase deficiency hemolytic anemia.
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PMID:Hemolytic anemia in hereditary pyrimidine 5'-nucleotidase deficiency: nucleotide inhibition of G6PD and the pentose phosphate shunt. 628 44

Oxidative stress and adenine nucleotide catabolism occur concomitantly in several disease states, such as cardiac ischaemia-reperfusion, and may act as synergistic determinants of tissue injury. However, the mechanisms underlying this potential interaction remain ill-defined. We examined the influence of oxidative stress on the molecular, kinetic and regulatory properties of a ubiquitous AMP-catabolizing enzyme, adenylate deaminase (AMPD) (EC 3.5.4.6). To this intent, rabbit heart AMPD and an H2O2/ascorbate/iron oxidation system were employed. Enzyme exposure to the complete oxidation system acutely impaired its catalytic activity, lowered the Vmax. by 7-fold within 5 min, and rendered the enzyme unresponsive to nucleotide effectors. Irreversible AMPD inactivation resulted within about 15 min of oxidative insult and was not prevented by free-radical scavengers. Oxidative stress did not affect the molecular mass, tetrameric nature, Km, immunoreactivity or trypsinolytic pattern of the enzyme; nor did it induce carbonyl formation, Zn2+ release from the holoenzyme or net AMPD S-thiolation. This injury pattern is inconsistent with a radical-fragmentation mechanism as the basis for the oxidative AMPD inactivation observed. Rather, the sensitivity of the enzyme to both S-thiolation and thiol alkylation and the significant (3 of 9/mol of denatured enzyme) net loss of DTNB-reactive thiols on exposure to oxidant strongly implicate the conversion of essential thiol moieties into stable higher-oxidation states in the oxidative inactivation of cardiac AMPD. The altered thiol status of the enzyme on oxidative insult may prohibit a catalytically permissible conformation and, in so doing, increase AMP availability to 5'-nucleotidase in vivo.
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PMID:Oxidative modulation and inactivation of rabbit cardiac adenylate deaminase. 788 95

The oxidative damage of proteins and lipid peroxidation of membrane lipoproteins has already been described as a possible pathogenic mechanism for liver injury. The aim of the present study was to examine the mechanism that could be responsible for the oxidative modification of rat liver 5'-nucleotidase during exposure to different free radical generating systems: FeCl2/ascorbate, xanthine/xanthine oxidase and H2O2. The level of lipid peroxidation products malondialdehyde (MDA), as well as the level of protein carbonyl groups formation was measured in cells and extracellular medium. The activity of 5'-nucleotidase was linearly decreased in both hepatocytes and extracellular medium after exposure to the FeCl2/ascorbate system indicating that the possible mechanism for oxidative modification could be a metal-binding site of the enzyme. In xanthine/xanthine oxidase system the enzyme activity of hepatocytes had decreased in hepatocytes but increased in the extracellular medium indicating that proteolysis of membrane proteins could he responsible for enzyme release in the extracellular medium. When hepatocytes were exposed to a H2O2 free-radical generating system, the activity of 5'-nucleotidase tended to be decreased in cells and decreased in extracellular medium too, indicating that H2O2 could be less reactive in producing an oxidative modification of the enzyme. In order to support the hypothesis that the cation-binding site can be responsible for oxidative modification of the enzyme, the isolated hepatocytes were preincubated with a Ca(2+)-channel blocker (Verapamil) and then exposed to different radical-generating systems. Verapamil had only a slight effect in potentiating the inhibition in the FeCl2/ascorbate system. This probably means that the cellular cation flux and cation binding may be included as a vulnerable site with the greatest importance in the oxidative modification of 5'-nucleotidase.
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PMID:The possible importance of the cation-binding site for the oxidative modification of liver 5'-nucleotidase. 989 65

Theoretically, zinc can exert a number of indirect antioxidant functions. Researchers at our laboratory have found evidence to support this concept by studying mild zinc deficiency in rats. This state produces low resistance to chemically induced liver oxidant injury, and it produces high vulnerability of lipoproteins to oxidation. We are building on this work in rats to test a hypothesis in humans that increased zinc intake will protect against oxidant stress in persons with tendencies for both moderate zinc deficiency and high oxidant stress. This hypothesis has been tested in postmenopausal, type 2 diabetic women. A 3-wk supplementation with zinc (30 mg/d as glycine-chelate) raised initially low plasma zinc values to above normal values and increased plasma activities of 5'-nucleotidase. However, the latter values were still well below normal. Lipoprotein oxidation tendencies, a measure of oxidant stress, were not altered by the zinc treatment. A new project has been initiated to determine whether both a higher dose and longer duration of zinc treatment will normalize 5'-nucleotidase activities and affect the indices of oxidant stress. The latter will be considered in terms of both zinc supplementation and supplementation of zinc plus vitamin C, another problem nutrient for diabetic persons.
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PMID:Zinc in relation to diabetes and oxidative disease. 1080 67

5'-Nucleotidase, responsible for the conversion of adenosine-5'-monophosphate into adenosine, was purified from bovine brain membranes, and subjected to oxidative inactivation. The 5'-nucleotidase activity decreased slightly after the exposure to either glutathione or Fe2+. The glutathione-mediated inactivation of 5'-nucleotidase was potentiated remarkably by Fe2+, but not Cu2+, in a concentration-dependent manner. Similarly, glutathione exhibited a concentration-dependent enhancement of the Fe2+-mediated inactivation. In comparison, the glutathione/Fe2+ system was much more effective than the ascorbate/Fe2+ system in inactivating the enzyme. In support of an intermediary role of superoxide ions or H2O2 in the action of glutathione/Fe2+ system, superoxide dismutase and catalase expressed a substantial protection against the inactivation by the glutathione/Fe2+ system. Meanwhile, hydroxyl radical scavengers such as mannitol, benzoate or ethanol were incapable of preventing the inactivation, excluding the participation of extraneous hydroxyl radicals. Whereas adenosine 5'-monophosphate as substrate exhibited a modest protection against the glutathione/Fe2+ action, a remarkable protection was expressed by divalent metal ions such as Zn2+ or Mn2+. Structure-activity study with a variety of thiols indicates that the inactivating action of thiols in combination with Fe2+ resides in the free sulfhydryl group and amino group of thiols. Overall, thiols, expressing more inhibitory effect on the activity of 5'-nucleotidase, were found to be more effective in potentiating the Fe2+-mediated inactivation. Further, kinetic analyses indicate that Fe2+ and thiols inhibit the 5'-nucleotidase in a competitive or uncompetitive manner, respectively. These results suggest that ecto-5'-nucleotidase from brain membrane is one of proteins susceptible to thiols/Fe2+-catalyzed oxidation, and the oxidative inactivation may be related to the selective association of Fe2+ and thiols to the enzyme molecule.
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PMID:Oxidative inactivation of brain ecto-5'-nucleotidase by thiols/Fe2+ system. 1107 66

Oxidative stress is implicated in the pathogenesis of diabetes mellitus. Selenium supplementation has some benefits in experimental models of diabetes mellitus. This study evaluated whether dietary diphenyl diselenide, a simple synthetic organoselenium compound with antioxidant properties, reduces the streptozotocin (STZ)-induced toxicity. STZ-induced diabetic rats were fed with either standard and diphenyl diselenide (10 ppm) supplemented diets. In experimental trials, dietary diphenyl diselenide significantly decreased mortality rate (p<0.05) induced by STZ treatment. No correlation between this effect and glycemic levels were found. Diphenyl diselenide intake also promoted an increase in vitamin C, -SH levels (liver, kidney and blood) and in catalase (liver and kidney) activity, which were decreased in STZ-treated rats. In enzyme assays, diphenyl diselenide supplementation caused a significant improvement in platelets NTPDase and 5'-nucleotidase activities in STZ-induced diabetic rats when compared to the control and diabetic groups (p<0.05). Nevertheless, this supplementation did not modify the inhibition induced by STZ in delta-ALA-D activity. Our findings suggest that diphenyl diselenide compound showed beneficial effects against the development of diabetes by exhibiting antioxidant properties.
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PMID:Dietary diphenyl diselenide reduces the STZ-induced toxicity. 1787 Feb 24

Chemoprevention has emerged as a very effective preventive measure against carcinogenesis. Several bioactive compounds present in fruits and vegetables have revealed their cancer curative potential on benzo(a)pyrene (B(a)P) induced carcinogenesis. In the present study, the efficacy of quercetin on the level of lipid peroxides, activities of antioxidant enzymes and tumor marker enzymes in B(a)P induced experimental lung carcinogenesis in Swiss albino mice was assessed. In lung cancer bearing animals there was an increase in lung weight, lipid peroxidation and marker enzymes such as aryl hydrocarbon hydroxylase, gamma glutamyl transpeptidase, 5'-nucleotidase, lactate dehydrogenase and adenosine deaminase with subsequent decrease in body weight and antioxidant enzymes-superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, glutathione reductase, reduced glutathione, vitamin E and vitamin C. Quercetin supplementation (25 mg/kg body weight) attenuated all these alterations, which indicates the anticancer effect that was further confirmed by histopathological analysis. Overall, the above data shows that the anticancer effect of quercetin is more pronounced when used as an chemopreventive agent rather than as a chemotherapeutic agent against B(a)P induced lung carcinogenesis.
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PMID:The effects of quercetin on antioxidant status and tumor markers in the lung and serum of mice treated with benzo(a)pyrene. 1805 10