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 activities of hexokinase, glucokinase, phosphofructokinase, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, and fructose-1,6-diphosphatase were determined in loach embryos developed in solutions of insulin, hydrocortisone, estrone and thyroxin at different stages of embryogenesis. Glucokinase and fructose-1,6-diphosphatase activties are shown not to change markedly under the influence of the above-mentioned hormones. During some periods of early development the hexokinase activity is inhibited by insulin, estrone and thyroxin. The glucose-6-phosphate dehydrogenase activity is suppressed by each of the used hormones at all the stages of early embryogenesis while the glocose-6-phosphatase activity decreased only under the influence of insulin at the cleavage, blastula and gastrula stages. Insulin increased the activity of phosphofructokinase at the cleavage, blastula and early gastrula stages and hydrocortisone, estrone and thyroxine during certain periods of these stages. From middle gastrula two last hormones decreased the phosphofructokinase activity in the loach embryos.
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PMID:[Activity of carbohydrate metabolism enzymes in loach embryos under the influence of hormones]. 19 80

1. Glucokinase was absent from chicken liver and only the low Km hexokinases, inhibited by AMP, ADP but not ATP, were present. 2. The Km of chicken liver glucose-6-phosphatase for glucose-6-phosphate was reduced from 5.65 to 3.75 mM following starvation, and the enzyme was inhibited by glucose. 3. Starvation of chickens for 24 hr slightly lowered the hexokinase activity and doubled glucose-6-phosphatase activity; it did not change subcellular distribution of the enzymes. Oral glucose rapidly restored the activities to fed values. 4. It was concluded that glucose uptake into, and efflux from, chicken hepatocytes, was regulated by the activity and kinetic characteristics of glucose-6-phosphatase and by the glucose-6-phosphate concentration, and that the hexokinases had little regulatory function.
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PMID:Glucose phosphorylation and dephosphorylation in chicken liver. 23 87

Carbohydrate intolerance was investigated in 8 alcoholics with liver cirrhosis and in controls. Indices of carbohydrate metabolism, glucose and insulin levels after glucose loading, were compared with glucose phosphorylating (glucokinase, hexokinase) and releasing (glucose-6-phosphatase) enzymes. Comparison was also made with pericellular collagen in liver biopsies and with insulin sensitivity assessed by the euglycemic clamp technique and with conventional liver function tests including oral antipyrine test. Glucokinase activity was low or absent, hexokinase activity increased and the GK/HK ratio reduced. Glucose-6-phosphatase activity was lowered and insulin sensitivity decreased. Pericellular collagen was increased (P less than 0.001) and related to the fasting glucose (r0.593) and insulin levels (r0.526). Blood glucose was related to antipyrine metabolism (r-0.727) but not to the other liver tests. Glucose intolerance in cirrhosis seems to be associated with reduced glucose phosphorylating and liberating enzyme activities. Hyperinsulinaemia, developing secondarily, may then lead to insulin resistance.
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PMID:Carbohydrate intolerance associated with reduced hepatic glucose phosphorylating and releasing enzyme activities and peripheral insulin resistance in alcoholics with liver cirrhosis. 299 23

In diabetic rats transplanted with fetal pancreata we measured the activities of six important enzymes to assess the return of liver metabolism to normal. Comparison was made among the responses of transplanted rats with and without renal-portal vein shunts and of those not transplanted and injected with insulin in varying doses. Insulin supply was not limited since three or four fetal pancreata were first grown in normal rats before transfer into the diabetic animals. Transplantation normalized blood and urine glucose and the rate of disappearance of intravenous glucose. Glucokinase and pyruvate kinase activities in liver rose toward normal at 7 days after transplantation and reached normal levels at 30 and 90 days. The response of the other four enzymes, glucose-6-phosphate dehydrogenase, citric lyase, fructose-1,6-bisphosphatase, and glucose-6-phosphatase, was more rapidly restored to normal at 7 days and remained normal at 30 and 90 days. No difference was observed in the enzyme activities of transplanted-shunted rats to nonshunted animals. Glucokinase activity was restored to normal after 1 wk of daily injections of 1 U of PZI; pyruvate kinase restoration required 3 U/day. Glucose-6-phosphate dehydrogenase and citric lyase required 2 U/day to be restored to normal; 3 U daily resulted in temporary supernormal activities. The gluconeogenic enzymes, fructose-1,6-bisphosphatase and glucose-6-phosphatase, were only partially suppressed toward normal by insulin even with 3 U daily for 3 wk. These findings indicate that pancreas transplantation is a more effective regulator of liver metabolism in diabetes than insulin injections.
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PMID:Normalization of six key hepatic enzymes after fetal pancreas transplantation in diabetic rats. 630 89

The probable involvement of hepatic carbamyl-P in the reciprocal relationship between hepatic ureagenesis and glycogenesis from glucose was explored. Isolated perfused liver preparations from 48-h fasted rats were employed. Moderate (9.2 mM) and relatively high levels of glucose (34 mM) were perfused. Hepatic glycogenesis, glucose-6-P, carbamyl-P, and citrulline levels, hepatic urea formation, and ureagenesis based upon perfusate urea levels were measured. Experimental probes selected to modify hepatic ureagenesis and carbamyl-P production and utilization included: (a) NH4Cl, maintained at 5 mM by continuous infusion (NH4+ is a substrate for carbamyl-P synthase I and glutamate dehydrogenase); (b) norvaline, an inhibitor of ornithine transcarbamylase which catalyzes the first committed step in the urea cycle; and (c) ethoxyzolamide, an inhibitor of carbonic anhydrase which produces HCO3-, an essential substrate for carbamyl-P synthase I. NH4+ increased ureagenesis and decreased glycogenesis. The inclusion of norvaline with NH4+ decreased ureagenesis and increased glycogenesis. Ethoxyzolamide with or without NH4+ inhibited both ureagenesis and glycogenesis, and decreased the hepatic glucose-6-P level. Glycogenesis was greater at 34 mM than 9.2 mM glucose, increased in norvaline-containing preparations correlative with increased availability of carbamyl-P, and decreased when carbamyl-P formation was inhibited by ethoxyzolamide. Kinetic analysis indicated a Km, Glc of 31 mM for glucose phosphorylation preliminary to glycogenesis. Glycogen formation via the "indirect pathway" (i.e. involving extrahepatic glycolysis, transport of lactate to the liver, and glyconeogenesis therefrom) was quantitatively insufficient to account for the observed glycogenesis. Glucokinase is contraindicated by the inverse relationship between hepatic glycogenesis and ATP availability in the ethoxyzolamide-treated preparations. In contrast, carbamyl-P:glucose phosphotransferase activity of the glucose-6-phosphatase system has the characteristics to bridge hepatic ureagenesis and glycogenesis.
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PMID:Glycogenesis from glucose and ureagenesis in isolated perfused rat livers. Influence of ammonium ion, norvaline, and ethoxyzolamide. 813 5

Increased hepatic glucose production (HGP) is the major cause of fasting hyperglycemia in all forms of diabetes. Glucokinase (GK) and glucose-6-phosphatase (Glc-6-Pase) are the proximal and the distal enzymatic steps, respectively, in the regulation of HGP. We examined the impact of changes in GK and Glc-6-Pase activities on in vivo hepatic glucose fluxes in diabetic (D) and control (C) rats. In particular, the acute regulation by insulin was investigated using the euglycemic hyperinsulinemic clamp technique in conscious rats. In experimental diabetes (6 weeks): (a) GK mRNA was decreased by approximately 40%; (b) the Vmax of GK was markedly decreased (approximately 4 versus 9 mumol/g wet weight/min) and that of Glc-6-Pase was 2-fold increased (approximately 30 versus 15 mumol/g wet weight/min, D versus C), while (c) the Km of GK (approximately 10 mM) and Glc-6-Pase (approximately 1.5 mM) were unchanged. HGP was increased by 65% in diabetes and correlated highly with the ratio of Glc-6-Pase/GK (r = 0.81, p < 0.01). Following acute hyperinsulinemia (2 h): (a) GK mRNA increased by approximately 2-fold in both C and D; (b) GK Vmax did not change in C, but doubled to near-normal in D; (c) Glc-6-Pase Vmax decreased by 23% in C and by 34% in D; (d) the Km of GK decreased by approximately 40% (p < 0.01) in C. Acute hyperinsulinemia almost completely inhibited HGP in both C and D, and no correlation was demonstrated between HGP and the ratio of Glc-6-Pase/GK in these groups. Our data suggest that GK and Glc-6-Pase are important determinants of fasting HGP in diabetes. However, acute changes in Glc-6-Pase and GK activities can account for only a small portion of the in vivo inhibition of hepatic glucose flux by insulin, suggesting additional mechanisms for the short-term regulation of HGP.
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PMID:Role of glucokinase and glucose-6-phosphatase in the acute and chronic regulation of hepatic glucose fluxes by insulin. 822 65

Glucose-6-phosphatase, a key enzyme in the homeostatic regulation of blood glucose concentration, catalyzes the terminal step in gluconeogenesis and glycogenolysis. Glucose, the product of the glucose-6-phosphatase reaction, dramatically increases the level of glucose-6-phosphatase mRNA transcripts in primary hepatocytes (20-fold), and the maximum response is obtained at a glucose concentration as low as 11 mM. Glucose specifically increases glucose-6-phosphatase mRNA and L-type pyruvate kinase mRNA. In the rat hepatoma-derived cell line, Fao, glucose increases the glucose-6-phosphatase mRNA only modestly (3-fold). In the presence of high glucose concentrations, overexpression of glucokinase in Fao cells via recombinant adenovirus vectors increases lactate production to the level found in primary hepatocytes and increases glucose-6-phosphatase gene expression by 21-fold. Similar overexpression of hexokinase I in Fao cells with high levels of glucose does not increase lactate production nor does it change the response of glucose-6-phosphatase mRNA to glucose. Glucokinase overexpression in Fao cells blunts the previously reported inhibitory effect of insulin on glucose-6-phosphatase gene expression in these cells. Raising the cellular concentration of fructose-2,6-bisphosphate, a potent effector of the direction of carbon flux through the gluconeogenic and glycolytic pathways, also stimulated glucose-6-phosphatase gene expression in Fao cells. Increasing the fructose-2,6-bisphosphate concentration over a 15-fold range (12 +/- 1 to 187 +/- 17 pmol/plate) via an adenoviral vector overexpression system, led to a 6-fold increase (0.32 +/- 0. 03 to 2.2 +/- 0.33 arbitrary units of mRNA) in glucose-6-phosphatase gene expression with a concomitant increase in glycolysis and a decrease in gluconeogenesis. Also, the effects of fructose-2, 6-bisphosphate concentrations on fructose-1,6-bisphosphatase gene expression were stimulatory, leading to a 5-6-fold increase in mRNA level over a 15-fold range in fructose-2,6-bisphosphate level. Liver pyruvate kinase and phosphoenolpyruvate carboxykinase mRNA were unchanged by the manipulation of fructose-2,6-bisphosphate level.
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PMID:Stimulation of glucose-6-phosphatase gene expression by glucose and fructose-2,6-bisphosphate. 913 47

Activities of enzymes related to glucose metabolism were measured in canine and feline liver. There were no significant differences in plasma glucose and immunoreactive insulin concentrations between dogs and cats. Glucokinase activities were absent in feline liver, however, activities of other glycolytic enzymes such as hexokinase, phosphofructokinase and pyruvate kinase, were significantly higher than those in canine livers. Activities of rate limiting enzymes of gluconeogenesis such as pyruvate carboxylase, fructose-1, 6-bisphosphatase and glucose-6-phosphatase in feline livers were significantly higher than those in canine livers.
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PMID:Comparison of the activities of enzymes related to glycolysis and gluconeogenesis in the liver of dogs and cats. 1050 95

The inhibitory effects of the traditional herbal medicine Jindangwon (JDW) on streptozotocin (ST)-induced diabetic mellitus were studied using the ST-treated diabetic model. Glucokinase activity of pancreatic islets was severely impaired by ST treatment. However, when ST-treated islets were treated with 1 mg/ml of JDW, the enzyme activities of glucokinase and hexokinase were protected, glucose-6-phosphatase was not. When the effects of JDW on ST-induced ATP/ADP ratio of islets were assayed, JDW was effective in restoring of ATP/ADP ratio. In addition, ST decreased the enzyme activities of PDH, while JDW had a protective effect on the enzyme. ST-induced cGMP accumulation was significantly inhibited by JDW treatment. Furthermore, ST-induced nitrite formation was significantly inhibited by JDW treatment. JDW also showed the suppressed nitrite production in ST-treated pancreatic islet cells. When the islets (200/condition) were treated with ST (5 mM for 30 min), and then JDW was added to the ST-treated cells, 1.0 mg/ml of JDW showed the activated and recovered aconitase activity in pancreatic islet cells. When the effect of ST on the gene expression of pancreatic GLUT2 and glucokinase were examined, the level of GLUT2 and glucokinase mRNA in pancreatic islets was significantly decreased. However, JDW protected and improved the expression of protein and genes, indicating that JDW is effective on ST-induced inhibition of gene expression of GLUT2, glucokinase and proinsulin in islets. These results suggested that JDW is effective in this model to treat ST-induced diabetes.
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PMID:Effect of Jindangwon on streptozotocin-induced diabetes. 1097 94

The development of Dictyostelium discoideum is a model for tissue size regulation, as these cells form groups of approximately 2 x 10(4) cells. The group size is regulated in part by a negative feedback pathway mediated by a secreted multipolypeptide complex called counting factor (CF). CF signal transduction involves decreasing intracellular CF glucose levels. A component of CF, countin, has the bioactivity of the entire CF complex, and an 8-min exposure of cells to recombinant countin decreases intracellular glucose levels. To understand how CF regulates intracellular glucose, we examined the effect of CF on enzymes involved in glucose metabolism. Exposure of cells to CF has little effect on amylase or glycogen phosphorylase, enzymes involved in glucose production from glycogen. Glucokinase activity (the first specific step of glycolysis) is inhibited by high levels of CF but is not affected by an 8-min exposure to countin. The second enzyme specific for glycolysis, phosphofructokinase, is not regulated by CF. There are two corresponding enzymes in the gluconeogenesis pathway, fructose-1,6-bisphosphatase and glucose-6-phosphatase. The first is not regulated by CF or countin, whereas glucose-6-phosphatase is regulated by both CF and an 8-min exposure to countin. The countin-induced changes in the Km and Vmax of glucose-6-phosphatase cause a decrease in glucose production that can account for the countin-induced decrease in intracellular glucose levels. It thus appears that part of the CF signal transduction pathway involves inhibiting the activity of glucose-6-phosphatase, decreasing intracellular glucose levels and affecting the levels of other metabolites, to regulate group size.
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PMID:Exposure of cells to a cell number-counting factor decreases the activity of glucose-6-phosphatase to decrease intracellular glucose levels in Dictyostelium discoideum. 1564 62


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