Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The metal-binding agents (citrate, oxalate, bicarbonate, EDTA) exert dual effects on D-glucose-6-phosphate phosphohydrolase activity in the homogenate as well as in the subcellular fractions. The important differences of the effects are associated with the concentration of the chelator and with time of its addition. The small (appropriate) concentrations of the metal-binding agents stimulate and stabilize the enzyme activity. However, chelators used in higher concentrations exert the inhibitory influence on the activity of glucose-6-phosphatase. Stimulation of the reaction was observed only if the chelator was added before the enzyme-substrate complex formation has been started. The formation of the ternary complex: the enzyme(metal)-chelator substrate exerting a protective influence on the active centre has been suggested. The hypothesis of a similar action of the metal-binding agents and Pi on the glucose-6-phosphatase as a metaloproteid has been proposed.
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PMID:Differential effects of metal-binding agents on the D-glucose-6-phosphate phosphohydrolase activity of the rat liver. 16 76

To evaluate some of the early effects of methymercury chloride (MMC) male rats were given 10, 20 or 30 mg MMC/kg intraperitoneally. Urine was analysed for vanilmandelic acid (VMA), leucine aminopeptidase (LAP), alkaline phosphatase (AP), and creatinine, blood for glucose-6-phosphatase (G-6-P) and glucose, serum for glutamate-oxalate-transaminase (GOT) and urea. Except for LAP and AP excretion there is no effect of MMC on the parameters investigated. However, the effects on these 2 renal enzymes are to variable to permit their use as a test for MMC toxicity.
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PMID:Effect of methylmercury on some constituents of serum and urine. 71 3

DL alpha-lipoic acid has been shown to prevent the induced precipitation of calcium oxalate crystals in the renal tissues of laboratory animals. The acid seems to have a profound influence on carbohydrate metabolism in diabetic rats. Here the effect of alpha-lipoic acid was studied on certain key carbohydrate metabolising enzymes in the tissues of calcium oxalate stone forming rats administered with glycollate as oxalate precursor. There was augmentation of glycolysis in the renal tissues of stone forming as well as lipoate administered rats. The two major gluconeogenic enzymes, glucose-6-phosphatase (G6P) and fructose-1, 6 diphosphatase (FDP) were significantly inhibited in tissues of calculogenic rats. Lipoic acid also reduced the enzyme activities significantly. The citric acid cycle enzymes were not influenced to an appreciable extent. The observed alterations are likely to be due to the regulatory effects of oxalate and lipoate on the enzyme systems.
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PMID:Effect of DL alpha-lipoic acid on some carbohydrate metabolising enzymes in stone forming rats. 166 49

We have recently shown that the Ca.EGTA and Mg.EDTA complexes, but not free Ca2+ or Mg2+, inhibit the liver glucose-6-phosphatase (Mithieux, G., Vega, F. V., Beylot, M., and Riou, J. P. (1990) J. Biol. Chem. 265, 7257-7259). In this work, we report that, when complexed with Mg2+, two endogenous dicarboxylic keto acids (alpha-ketoglutarate (alpha-KG) and oxaloacetate (OAA] inhibit the glucose-6-phosphatase activity at low concentrations of substrate. This phenomenon is specific for complexes of Mg2+ with alpha-KG and OAA since 1) the complexes of Mg2+ with a number of other di- or tricarboxylic acids having high structural analogy with alpha-KG and OAA (oxalate, malate, succinate, citrate, aspartate, and glutamate) do not inhibit the glucose-6-phosphatase activity and 2) the Ca.alpha-KG and Ca.OAA chelates do not inhibit the glucose-6-phosphatase activity. In the presence of Mg.alpha-KG or Mg.OAA chelates, the enzyme displays sigmoid kinetics; the Hanes plots deviate from linearity, indicating the positive cooperative dependence of the velocity upon the substrate concentration. Hill coefficients (equal to 1 in the absence of the chelates) of 1.23 and 1.33 have been determined in the presence of Mg.alpha-KG and Mg.OAA complexes, respectively. The disruption of microsomal integrity by detergents abolishes the effect of Mg.alpha-KG and Mg.OAA, suggesting that the magnesium chelates inhibit the translocase component of the glucose-6-phosphatase system.
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PMID:The liver glucose-6-phosphatase of intact microsomes is inhibited and displays sigmoid kinetics in the presence of alpha-ketoglutarate-magnesium and oxaloacetate-magnesium chelates. 217 3

Mechanisms regulating the energy-dependent calcium sequestering activity of liver microsomes were studied. The possibility for a physiologic mechanism capable of entrapping the transported Ca2+ was investigated. It was found that the addition of glucose 6-phosphate to the incubation system for MgATP-dependent microsomal calcium transport results in a marked stimulation of Ca2+ uptake. The uptake at 30 min is about 50% of that obtained with oxalate when the incubation is carried out at pH 6.8, which is the pH optimum for oxalate-stimulated calcium uptake. However, at physiological pH values (7.2-7.4), the glucose 6-phosphate-stimulated calcium uptake is maximal and equals that obtained with oxalate at pH 6.8. The Vmax of the glucose 6-phosphate-stimulated transport is 22.3 nmol of calcium/mg protein per min. The apparent Km for calcium calculated from total calcium concentrations is 31.9 microM. After the incubation of the system for MgATP-dependent microsomal calcium transport in the presence of glucose 6-phosphate, inorganic phosphorus and calcium are found in equal concentrations, on a molar base, in the recovered microsomal fraction. In the system for the glucose 6-phosphate-stimulated calcium uptake, glucose 6-phosphate is actively hydrolyzed by the glucose-6-phosphatase activity of liver microsomes. The latter activity is not influenced by concomitant calcium uptake. Calcium uptake is maximal when the concentration of glucose 6-phosphate in the system is 1-3 mM, which is much lower than that necessary to saturate glucose-6-phosphatase. These results are interpreted in the light of a possible cooperative activity between the energy-dependent calcium pump of liver microsomes and the glucose-6-phosphatase multicomponent system. The physiological implications of such a cooperation are discussed.
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PMID:Calcium sequestration activity in rat liver microsomes. Evidence for a cooperation of calcium transport with glucose-6-phosphatase. 298 15

Calcium uptake and binding activities of microsomal fractions from bovine coronary artery and aorta were examined. The isolated microsomal fraction of the coronary artery and aorta showed 7- to 8-fold higher glucose-6-phosphatase activity and 4- to 6-fold higher NADPH-cytochrome c reductase activity as compared with the corresponding values for the homogenate fraction. Coronary artery and aorta microsomal calcium uptake activities were 118 and 159 nmoles Ca2+/mg protein/10 min in the presence of 100 microM CaCl2, respectively. These activities for bovine vascular smooth muscle microsomes are higher than those of other species investigated. The calcium uptake activities were dependent on calcium concentrations ranging from 5 to 50 microM in the assay medium. The onset of the reaction for aorta microsomal calcium uptake was faster than that for the coronary artery. The calcium uptake activity was also dependent on ATP, but it was practically independent of oxalate ions in the assay medium. Microsomal calcium binding activities of the coronary artery and aorta were maximal at 20 min of incubation under the present experimental conditions. A lower Km value of the aortic calcium binding for ATP was obtained as compared with that for the coronary artery. The present experiment explored several characteristics of the microsomal calcium-accumulating ability of vascular smooth muscle, which provides meaningful information for further study on cellular calcium movements in vascular smooth muscle.
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PMID:Microsomal calcium-accumulating ability of bovine coronary artery and aorta. 299 Apr 86

The effect of cyclosporin A, a highly effective immunosuppressant, was investigated on hyperoxaluric rats with and without vitamin E pretreatment. Hyperoxaluria was induced by oral feeding of 3% ammonium oxalate in water for 3 days. Cyclosporin A (50 mg/kg body wt.) was administered for 3 days. Pretreatment with vitamin E (50 mg/100 g body wt., once a week for 3 weeks) was carried out before the administration of cyclosporin A and ammonium oxalate. Nonenzymatic ascorbate-induced lipid peroxidation was increased to 1.55-fold in either cyclosporin A-administered or hyperoxaluric rat kidney and liver when compared to control. The lipid peroxidation was further elevated to 1.9-fold when both cyclosporin A and ammonium oxalate were coadministered. The activities of renal and hepatic ATPase, glucose-6-phosphatase as well as the concentrations of thiols were decreased significantly (p < 0.001) when cyclosporin A was administered under hyperoxaluric condition. On pretreatment with vitamin E the cyclosporin A-induced biochemical changes observed in the presence of hyperoxaluria were abolished.
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PMID:Effect of cyclosporin A on tissue lipid peroxidation and membrane bound phosphatases in hyperoxaluric rat and the protection by vitamin E pretreatment. 935 65