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)

Five patients with glycogen storage disease are described. Hypoglycemia was observed in all patients after an overnight fast, and glycemic and lactatemic curves obtained after oral administration of glucose or galactose were typical of those seen in Type III glycogenosis. An increase of liver glycogen up to 12-16% and complete absence of liver amylo-1,6-glucosidase were found in liver tissue samples obtained by needle biopsy. The patients were diagnosed as having Type III glycogenosis. In two patients the absence of amylo-1,6-glycosidase was accompanied by a sharp decline of liver phosphorylase activity. In one patient a decline of glucose-6-phosphatase activity was observed. The structure of liver glycogen was different in different patients, and so were the types of glycemic and lactatemic curves obtained upon protein tolerance tests. The above phenomena might be explained by some secondary disturbances in the activity of enzymes (phosphorylase, glucose-6-phosphatase) involved in the metabolism of liver glycogen of these patients.
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PMID:Some cases of Type III glycogen storage disease. 106 45

Insluin injected intravenously caused a rapid, marked decrease in hepatic glucose secretion in the rabbit, as determined by an isotope-dilution procedure. This was associated with a decrease in the concentrations of gluconeogenic intermediates from phosphoenolpyruvate to triose phosphates, inclusive, compatible with inhibition of gluconeogenesis at phosphoenolpyruvate carboxykinase. The concentration of glucose 6-phosphate was unaltered but that of hepatic glucose was reduced. The specific activities of the hexose phosphates, relative to that of liver glucose, were the same in control and insulin-treated animals. These observations can be explained by a decrease in the activity of glucose-6-phosphatase. It is concluded that this enzyme is a control point for hepatic glucose production and is inhibited by insulin. In the rat, insulin produced a rapid fall in blood sugar. The hepatic glucose output remained normal despite a fall in hepatic glucose 6-phosphate concentration during the initial period of insulin action. This suggests that glucose-6-phosphate returned to normal with no change in the rate of glucose production. The data suggest that in the rat, insulin produces a transient increase in glucose-6-phosphatase activity.
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PMID:Insulin control of hepatic glucose production. 112 Feb 88

In vitro rates of lactate conversion to glucose and oxidation to CO2 were determined in livers of stress-susceptible (SS) and stress-resistant (SR) pigs because we hypothesized that livers of SS pigs had a lower capacity than livers of SR pigs to remove lactate from blood. Stress-susceptibility was determined by reaction to halothane at 7 weeks of age. At approximately 9 weeks of age, pigs were assigned to one of three experimental diets. Pigs weighing 95 kg were slaughtered immediately after stress, and liver samples were obtained. Incorporation of lactate into glucose in liver of SS pigs was 38% of that in SR pigs. Addition of either vitamin C or vitamins C and E plus magnesium oxide and collagen extract to a corn-soy diet did not alter lactate conversion to glucose, but depressed lactate oxidation to CO2. No differences were detected in either activities of lactate dehydrogenase, HAD-malate dehydrogenase, phosphoenolpyruvate carboxykinase, fructose-1,6-diphosphatase, and glucose-6-phosphatase or concentration of glycogen in livers of SS and SR pigs. Our data indicate that livers of SS pigs possess a lower capacity to incorporate lactate into glucose and to oxidize lactate to CO2; maximal activities of enzymes measured in this study are not the cause of these differences. Reduced capacity of lactate metabolism in livers of SS pigs seems a part of the etiology of the porcine stress syndrome.
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PMID:Gluconeogenesis from lactate in liver of stress-susceptible and stress-resistant pigs. 126 79

The availability of a rare set of human hepatic microsomes in which T2, a pyrophosphate/phosphate transport protein of the glucose-6-phosphatase system, has been shown immunologically to be completely absent, has permitted further characterization of multicomponent glucose-6-phosphatase (EC 3.1.3.9). Pyrophosphatase activity in intact microsomes was found to be totally absent, but was normal in disrupted microsomes. However, Pi did not accumulate within the lumen of the microsomes when glucose 6-phosphate was the substrate. This was not as predicted if there is only one transport protein in the endoplasmic reticulum capable of transporting Pi, produced by glucose-6-phosphatase, out of the lumen. The results suggest that the pyrophosphate/phosphate transport system of human hepatic endoplasmic reticulum must be more complex than previously thought, as it must comprise at least two protein components.
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PMID:Analysis of human hepatic microsomal glucose-6-phosphatase in clinical conditions where the T2 pyrophosphate/phosphate transport protein is absent. 131 Nov 77

Corticosterone and cortisol administered to Calotes versicolor significantly increased the concentrations of blood glucose and urea (liver and kidney), the specific activities of glucose-6-phosphatase (liver and kidney), and glutamic oxaloacetic transaminase (liver and heart); they markedly reduced hepatic cholesterol level and did not change the activities of acid phosphatase (liver and kidney) and glutamic pyruvic transaminase (liver), when compared to vehicle-treated controls.
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PMID:A comparison of the effects of corticosterone and cortisol on intermediary metabolism of Calotes versicolor. 131 6

A preferential impairment of the pancreatic B cell secretory response to D-glucose occurs in adult rats injected with streptozotocin during the neonatal period. Three possible explanations for such a preferential defect were investigated in the present study. First, the time course for 3-O-methyl-D-glucose uptake by islets suggested that the anomaly in hexose transport was mainly attributable to a decrease in the space accessible to the D-glucose analog commensurate with the decrease in B cell mass, rather than to a delayed equilibration of hexose concentration across the B cell plasma membrane. Second, the activity of glucose-6-phosphatase was found to be equally low in islets from diabetic and control rats, ruling out the futile cycling between D-glucose and D-glucose 6-phosphate as a cause for the preferential alteration of the secretory response to the hexose. Third, the activity of flavine adenine dinucleotide-linked glycerophosphate dehydrogenase was found to be decreased to a greater relative extent than the B cell mass. This coincided with an impaired generation of 3HOH from L-[2-3H] glycerol in intact islets. It is proposed, therefore, that an altered circulation in the glycerol phosphate shuttle may play a major role in the impaired process of glucose-stimulated insulin release in this model of noninsulin-dependent diabetes.
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PMID:Enzymic and metabolic anomalies in islets of diabetic rats: relationship to B cell mass. 131 52

The effects of single acute oral doses of 1, 2.1, and 3.5 mg/kg oxamyl (a carbamate insecticide) on selected biochemical parameters in male Sprague-Dawley rats were investigated. The animals exhibited significantly decreased weight gain when compared to control animals. The compound inhibited brain and blood acetylcholinesterase significantly in the first few hours of exposure. Liver glucose-6-phosphatase was inhibited substantially after 7 and 4 days at the levels of 2.1 and 3.5 mg/kg, respectively. Maximum inhibition of liver succinic acid dehydrogenase was noted after 1 day at the level of 1 mg/kg and after 6 hr at the level of 2.1 and 3.5 mg/kg. Significant changes in serum total lipids and glucose were observed when oxamyl was given at 2.1 and 3.5 mg/kg, but serum protein was not affected at any dose level. However, the absence of statistically significant effects between Days 7 and 14 in most of the investigated parameters is indicative of an overall moderate degree of toxicity of oxamyl following acute oral administration of the selected doses.
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PMID:Acute toxic effects of oxamyl in the rat. 131 38

We describe an automated, homogeneous, glucose oxidase-coupled method for the determination of glucose-6-phosphatase activity in tissue extracts. The method is based on measurement of the rate of glucose formation by the Trinder reaction, in which the end product is a quinoneimine dye which absorbs maximally at 505 nm and has a molar extinction coefficient of 5700. The incubation mixture contains 20 microL of tissue extract, 25 microL of 0.5 M phosphate buffer, pH 7.0, 175 microL of Trinder/glucose-6-phosphate reagent, and 30 microL of distilled water. After a delay period of 15 min, to exhaust any glucose endogenously present in the extract, glucose production from glucose-6-phosphate is monitored at 505 nm for 5 min in a centrifugal analyzer. The Km was 13 mM over a 10-fold range in glucose-6-phosphate concentration and the reaction was linear up to about 250 U/L. Within-run CV of the assay at activities of 48 and 190 U/L ranged between 2.5-5.0%. The between-run CV at 190 U/L was 5.1%.
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PMID:Homogeneous trinder-coupled assay for the determination of glucose-6-phosphatase activity in tissue extracts. 132 Apr 68

Administration of L-thyroxine (T4) to thyroidectomized Calotes versicolor significantly increased the activity of glucose-6-phosphatase (G-6-Pase) (liver and kidney), the concentrations of blood glucose and total protein (liver and kidney), and decreased hepatic cholesterol when compared to thyroidectomized lizards. Propranolol injections in thyroidectomized lizards increased the cholesterol concentration and did not change the other parameters. The activity of G-6-Pase and blood glucose content was stimulated, whereas the total protein and cholesterol contents were decreased after alloxan treatment. Administration of T4 to thyroidectomized animals pretreated with propranolol or alloxan significantly elevated the activity of G-6-Pase, the concentrations of blood glucose, and total protein, and reduced hepatic cholesterol level when compared to drug-treated lizards. From the results, it is evident that thyroid hormone has an independent stimulatory influence on intermediary metabolism in C. versicolor irrespective of the involvement of adrenaline or insulin.
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PMID:Role of thyroid hormone in intermediary metabolism of propranolol or alloxan-treated Calotes versicolor. 132 45

Some of the acute actions of insulin may be mediated by an enzyme-modulating inositol phosphate glycan, produced by the insulin-sensitive hydrolysis of glycosyl-phosphatidylinositol (GPI) that is structurally similar to a membrane protein anchor. An inositol glycan fragment from the structurally characterized Trypanosoma brucei variant surface glycoprotein GPI anchor is evaluated for insulin-mimetic antilipolytic activity. The fragment specifically and dose-dependently inhibits isoproterenol-stimulated lipolysis. Like the effect of insulin, glycan-induced antilipolysis is blocked by the low Km cAMP phosphodiesterase inhibitor imazodan (CI-914) and the serine/threonine phosphatase inhibitor, okadaic acid, suggesting that the activation of both cAMP phosphodiesterase and serine/threonine protein phosphatases are necessary. Moreover, this fragment causes a specific and dose-dependent inhibition of both microsomal glucose-6-phosphatase (EC 3.1.3.9) and cytosolic fructose-1,6-bisphosphatase (EC 3.1.3.11) activity. Additionally, direct addition of the glycan to hepatocytes caused marked inhibition of glucose production from pyruvate. These results suggest that the direct modification of the activities of these two gluconeogenic enzymes by an inositol glycan may play a role in the inhibition of glucose output by insulin and provide the first evidence for the insulin-mimetic properties of a chemically characterized inositol glycan.
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PMID:An inositol phosphate glycan derived from a Trypanosoma brucei glycosyl-phosphatidylinositol mimics some of the metabolic actions of insulin. 132 96


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