Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

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

2-Bromopalmitate and 2-bromopalmitoyl-CoA have been shown to inhibit a variety of enzymes and proteins associated with lipid metabolism. We found that both of the brominated compounds were non-competitive inhibitors of two microsomal activities of triacylglycerol biosynthesis, the mono- and diacylglycerol acyltransferases. With both compounds, the calculated Ki values were lower than the Km value for the palmitoyl-CoA substrate. In addition to inhibiting two other lipid synthetic activities, fatty acid CoA ligase and glycerol-3-P acyltransferase, 2-bromopalmitate and 2-bromopalmitoyl-CoA also inhibited two microsomal enzyme activities that are not related to lipid metabolism, NADPH cytochrome-c reductase and glucose-6-phosphatase. Inhibition of the three acyltransferases and fatty acid CoA ligase could be overcome by the addition of phospholipid vesicles, and 2-bromo[14C]palmitate readily labeled a large number of membrane-bound proteins as well as cytosolic proteins that had been solubilized in SDS. Thus, it appears likely that the inhibitory properties of the brominated compounds strongly depend on the effective concentration of the inhibitor within membranes rather than on any specific affinity for an acyl-chain binding region of the enzyme.
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PMID:2-Bromopalmitoyl-CoA and 2-bromopalmitate: promiscuous inhibitors of membrane-bound enzymes. 157 64

1. The regulation of renal gluconeogenesis was studied in rats made septic by a caecal ligation and puncture technique. 2. Blood glucose concentrations were not markedly different in septic rats, but lactate, pyruvate and alanine concentrations were markedly increased, compared with sham-operated rats. Conversely, blood ketone body concentrations were significantly decreased in septic rats. Both plasma insulin and glucagon concentrations were markedly elevated in response to sepsis. 3. The maximal activities of glucose-6-phosphatase (EC 3.1.3.9), fructose-1,6-bisphosphatase (EC 3.1.3.11), pyruvate carboxylase (EC 6.4.1.1) and phosphoenolpyruvate carboxykinase (EC 4.1.1.49) were markedly decreased in kidneys obtained from septic rats, suggesting diminished renal gluconeogenesis. 4. Renal concentrations of lactate, pyruvate and other gluconeogenetic intermediates were markedly elevated in septic rats, whereas those of acetyl-CoA and fructose 2,6-bisphosphate were decreased and unchanged, respectively. 5. The rate of gluconeogenesis from added lactate, pyruvate and glycerol was decreased in isolated incubated renal tubules from septic rats. 6. Sepsis decreased the arteriovenous concentration difference for glucose, lactate, and alanine. Septic rats showed decreased net rates of glucose production and net rates of removal of lactate and alanine as compared with sham-operated controls. 7. It is concluded that the diminished capacity for renal gluconeogenesis in septic rats could be the result of changes in the maximal activities or regulation of key non-equilibrium gluconeogenic enzymes or both, but the effect of other factors (e.g. toxins) has not been excluded.
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PMID:Metabolic regulation of renal gluconeogenesis in response to sepsis in the rat. 217 16

Kinetic studies of the histochemical and histoenzymatic behavior of rabbit pancreatic parenchymas were performed 5, 30 and 90 days after Wirsung duct ligation. In control pancreas, some enzyme activities (EA) were more prominent in Langerhans islets [glucose-6-phosphatase, glucose-6-phosphate dehydrogenase (DH), isocitrate DH, glycerol-3-phosphate DH, NADPH DH], others were strongly marked in acini and ducts (alkaline phosphatase, beta-glucuronidase, acid esterase aryl-sulfatase). Histochemical and enzyme abnormalities observed in experimental rabbits reflect the post-ligation degenerative and reactive processes in both exocrine and endocrine pancreas: (1) the decrease in Krebs cycle and pentose pathway linked EA and the increased lysosomal and acid phosphatase EA reflect early (day 5) degeneration and necrosis of islets and acini (day 30); (2) proliferative processes in developed ductal epithelia are shown by an increase in both glycolytic and lysosomal EA (days 30 and 90); (3) connective tissue neogenesis and interstitial fibrosis occurred as shown by activated beta-glucuronidase, aryl-sulfatase, alkaline phosphatase and increased ribonucleoproteins and glycoaminoglycans contents (day 30); (4) on day 90, the neoformed cell clusters presenting glucose-6-phosphatase positivity (B-cell marker) are seen in the pancreas remnant. At the same time, blood insulin level increases correlated with a decrease of hyperglycemia.
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PMID:Cell features in pancreas of prediabetic and diabetic rabbits after Wirsung duct ligation. Histochemical and histoenzymatic studies. 233 24

The method is suggested to isolate simultaneously microsomes and plasma membranes of neuroblastoma S 1300 N 18 cells by means of differential centrifugation in the step density gradient of Percoll/Ficoll with a high degree of purification determined from the activity of marker enzymes (acetyl cholinesterase Na+,K+-ATPase, alkali phosphatase, glucose-6-phosphatase, succinate-dehydrogenase, acid phosphatase) as well as from the content of DNA and RNA and with a sufficiently high protein yield. The purified fractions of microsomes and plasma membranes are established to contain no phosphatidyl glycerol and cardiolipin--safety markers of mitochondrial membrane purification. A degree of separation of microsomes, plasma membranes and proteins dissolved in cytosol may be estimated by the activity of the cholesterol-synthesizing system of enzymes with the use of sterol-transferring protein.
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PMID:[Rapid simultaneous isolation of microsomes and plasma membranes from neuroblastoma C 1300 N 18 cells]. 258 50

Glucose and lipid metabolism in the brain, liver and in a transplanted tumour were found to be variously altered within 2 to 3 h of administering single doses of the radiosensitizer Ro-03-8799 to normal and tumour-bearing mice. Hepatic lactate and glycerol-3-phosphate (G3P) levels were decreased but those of the ketone body beta-hydroxybutyrate (beta-HOBu) were raised. However, in the tumour, these levels were all enhanced. The lactate levels in brain remained relatively constant but both beta-HOBu and G3P levels were altered in a manner similar to that in the liver. The levels of glucose were approximately doubled in blood, brain and tumour, but whereas tumour G6P levels increased, those in the brain were lowered to below the limits of detection. Hepatic glucose levels were significantly decreased after 1 h but G6P levels were not affected. These changes could neither be related to inhibitory effects on hepatic glucokinase or brain hexokinase activity nor to limiting amounts of ATP in both tissues. However, the activity of glucose-6-phosphatase (G6P'ase) was distinctly raised in the liver and the hepatic glycogen stores were also rapidly lowered. Overall, the results suggest that Ro-03-8799 exerts a stimulatory effect on glucose production in the liver. In both liver and brain the levels of free fatty acids and phospholipids were increased whereas those of esterified fatty acids were lowered. Most importantly, the changes in metabolite levels affect the cellular redox couples; those of the cytosol (lactate/pyruvate; G3P/dihydroxyacetone phosphate (DAP] are directed towards the oxidised state in the liver but to a more reduced state in the tumour. The mitochondrial couple (beta-HOBu/acetoacetate (AcAc)) in both tissues is shifted towards the reduced state. These metabolic changes may result in an increase in the degree of hypoxia in the tumour and may well play an important role in the development of neuropathies.
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PMID:Effects on intermediary metabolism in mouse tissues by Ro-03-8799. 282 72

Glycerol, glycerol-3-phosphate (G3P), and dihydroxyacetone phosphate (DHAP) were evaluated as inhibitors of gluconeogenesis on rat liver enzymes in vitro, and for their effects on glucose formation in vivo in well-nourished and malnourished rats. DHAP was more potent as an inhibitor than G3P on fructose-1,6-diphosphatase (FDPase), phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6Pase). The I50 for DHAP was 2, 8, and 9 x 10(-3) M, respectively. No effect was observed on rat liver pyruvate carboxylase (PC). Glycerol was a weak inhibitor of FDPase and PEPCK, but did not inhibit PC and G6Pase. In vivo, when G3P was injected before a parenteral L-alanine (Ala) challenge, it produced a hypoglycemic effect in malnourished rats and a lesser, but noticeable, blood glucose level reduction in well-fed animals. Glycerol caused a smaller reduction in glucose formation from Ala. No comparable effects were observed after a fructose pretreatment. These results underscore the potential hypoglycemic effects of phosphorylated glycerol metabolites and identify the steps in gluconeogenesis where this action is exerted. The study also stresses the nutritional component in the glycerol intolerance syndrome, apparent from the far more severe effects observed in malnourished rats given G3P or glycerol prior to Ala.
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PMID:Regulation of gluconeogenesis by glycerol and its phosphorylated derivatives. 298 19

Type I glycogen storage disease (McKusick 23220), an inherited absence or deficiency of glucose-6-phosphatase (EC 3.1.3.9) activity in the liver, kidney and intestine, is associated with the accumulation of glycogen in those organs. Previous reports have shown that glucose-6-phosphatase exists in human placenta and that detection of a heterozygote for this disorder from placenta might be possible. Our finding of a normal glucose-6-phosphatase activity in a placenta from a patient at risk for type Ia glycogen storage disease prompted us to examine in more detail placental glucose-6-phosphatase. Unexpectedly, we found the properties of the placental enzyme differed from that in normal liver, and the placental enzyme hydrolyzed glucose-6-phosphate, mannose-6-phosphate, beta-glycerol phosphate and glucose-1-phosphate equally well. Our data suggest the enzyme deficient in type I glycogen storage disease cannot be detected in placenta.
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PMID:Liver-specific glucose-6-phosphatase is not present in human placenta. 302 46

Homogenates of either rat or mouse pancreatic islets, pure rat B cells or insulin-producing cells of the RINm5F line catalyzed the hydrolysis of D-glucose-6-phosphate. Relative to protein content, the enzymic activity, which was mainly associated with particulate rather than soluble subcellular material, was much lower in endocrine pancreatic cells than in liver. The rat islet enzyme differed from liver glucose-6-phosphate by its lower affinity for D-glucose-6-phosphate, its lower pH optimum, its greater relative efficiency towards L-glycerol-3-phosphate as distinct from D-glucose-6-phosphate, its restricted lability during exposure to pH 5.0, its inability to act as a glucose-6-phosphate:glucose phosphotransferase, and its insensitivity to inhibition by D-glucose. It is concluded that rat islet cells are virtually devoid of true glucose-6-phosphatase activity.
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PMID:Hexose metabolism in pancreatic islets. Absence of glucose-6-phosphatase in rat islet cells. 303 Aug 54

Growth retardation and lactic aciduria are well-known abnormalities in patients with a deficiency of either glucose-6-phosphatase or glucose-6-phosphate translocase. In 19 patients with glucose-6-phosphatase and two patients with glucose-6-phosphate translocase, growth retardation was quantified by calculating the height standard deviation score. The urinary excretion of lactate and some other metabolites was quantified by calculating the lactate/creatinine, 2-oxoglutarate/creatinine, citrate/creatinine, and glycerol/creatinine ratios in urine. Significant correlations were found between the lactate/creatinine ratio, the 2-oxoglutarate/creatinine ratio, and height SD score. Urinary lactate appeared to respond promptly to changes of the diet, while urinary 2-oxoglutarate responded only slowly, as did growth itself. The citrate/creatinine ratio and the glycerol/creatinine ratio were within the normal range and varied little. It was concluded that the urinary 2-oxoglutarate excretion primarily reflects the severity of the disease as expressed in stunted growth. Thus, while urinary lactate levels are more suitable for monitoring the diet, urinary 2-oxoglutarate levels can be used as an indication for intensive treatment with hyperalimentation.
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PMID:Urinary excretion of lactate, 2-oxoglutarate, citrate, and glycerol in patients with glycogenosis type I. 347 Jul 5


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