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 endogenous synthesis of cholesterol in hepatocyte nodules, induced in male Wistar rats, by a single dose of the hepatocarcinogen diethylnitrosamine followed by a selection procedure, was investigated and was compared with that in surrounding and control tissue. In addition, the activity of enzymes related to carbohydrate metabolism (glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glucose-6-phosphatase and pyruvate kinase), was measured. Hepatocyte nodules showed a striking increase in their capacity for synthesizing cholesterol, in comparison to surrounding and control tissues, and an enhancement in the activity of the pentose phosphate pathway, as indicated by increased activity of glucose-6-phosphate dehydrogenase and of 6-phosphogluconate dehydrogenase, and a concomitant decrease of glucose-6-phosphatase. The stimulation of cholesterol synthesis and of the pentose phosphate pathway was associated with increased incorporation of labelled thymidine into DNA. These data indicate that, among other metabolic disturbances, enhancement of cholesterol synthesis and of the pentose phosphate pathway, is accompanied by an increased proliferative capacity of hepatocyte nodules.
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PMID:Enhancement of cholesterol synthesis and pentose phosphate pathway activity in proliferating hepatocyte nodules. 402 34

1. The activities of gluconeogenic and glycolytic enzymes and the concentrations of citrate, ammonia, amino acids, glycogen, glucose 6-phosphate, acetyl-CoA, lactate and pyruvate were measured in kidney cortex of normal, diabetic, cortisone-treated and growth hormone-treated rats. 2. In kidney cortex of diabetic, cortisone-treated and growth hormone-treated rats the activities of glucose 6-phosphatase (EC 3.1.3.9), fructose 1,6-diphosphatase (EC 3.1.3.11) and phosphopyruvate carboxylase (EC 4.1.1.32) were increased. 3. The activities of glutamate dehydrogenase (EC 1.4.1.3), alanine aminotransferase (EC 2.6.1.2), aspartate aminotransferase (EC 2.6.1.10) and pyruvate carboxylase (EC 6.4.1.1) were increased in diabetic and cortisone-treated rats. In growth hormone-treated rats the activity of aspartate aminotransferase was depressed but those of the other three enzymes were unchanged. 4. The activity of hexokinase (EC 2.7.1.1) was not altered in any of these conditions. Phosphofructokinase (EC 2.7.1.11) activity was depressed only in growth hormone-treated rats. Pyruvate kinase (EC 2.7.1.40) activity was depressed in cortisone-treated and growth hormone-treated rats but unchanged in diabetic rats. 5. Amino acids, acetyl-CoA and glucose 6-phosphate contents were increased in rat kidneys in all these three conditions. Ammonia content was increased in diabetic and cortisone-treated rats but was markedly diminished in growth hormone-treated rats. 6. The [lactate]/[pyruvate] ratio was elevated in diabetic and cortisone-treated rats but unchanged in growth hormone-treated rats. Citrate content was increased in the kidney cortex of diabetic and growth hormone-treated rats but was unchanged in cortisone-treated rats. The activity of ATP citrate lyase (EC 4.1.3.8) was depressed in diabetic and growth hormone-treated rats but was increased in cortisone-treated rats. 7. Glycogen content was moderately elevated in growth hormone-treated rats and markedly elevated in diabetic rats, whereas no change in glycogen content was observed in cortisone-treated rats. Glycogen synthetase (EC 2.4.1.11) activity was unchanged in all these three conditions. Phosphorylase (EC 2.4.1.1) activity was not affected in cortisone-treated rats but was depressed in diabetic and growth hormone-treated rats.
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PMID:Evaluation of the rate-limiting steps in the pathway of glucose metabolism in kidney cortex of normal, diabetic, cortisone-treated and growth hormone-treated rats. 434 56

1. Measurements were made of the activities of the four key enzymes involved in gluconeogenesis, pyruvate carboxylase (EC 6.4.1.1), phosphoenolpyruvate carboxylase (EC 4.1.1.32), fructose 1,6-diphosphatase (EC 3.1.3.11) and glucose 6-phosphatase (EC 3.1.3.9), of serine dehydratase (EC 4.2.1.13) and of the four enzymes unique to glycolysis, glucokinase (EC 2.7.1.2), hexokinase (EC 2.7.1.1), phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40), in livers from starved rats perfused with glucose, fructose or lactate. Changes in perfusate concentrations of glucose, fructose, lactate, pyruvate, urea and amino acid were monitored for each perfusion. 2. Addition of 15mm-glucose at the start of perfusion decreased the activity of pyruvate carboxylase. Constant infusion of glucose to maintain the concentration also decreased the activities of phosphoenolpyruvate carboxylase, fructose 1,6-diphosphatase and serine dehydratase. Addition of 2.2mm-glucose initially to give a perfusate sugar concentration similar to the blood sugar concentration of starved animals had no effect on the activities of the enzymes compared with zero-time controls. 3. Addition of 15mm-fructose initially decreased glucokinase activity. Constant infusion of fructose decreased activities of glucokinase, phosphofructokinase, pyruvate carboxylase, phosphoenolpyruvate carboxylase, glucose 6-phosphatase and serine dehydratase. 4. Addition of 7mm-lactate initially elevated the activity of pyruvate carboxylase, as also did constant infusion; maintenance of a perfusate lactate concentration of 18mm induced both pyruvate carboxylase and phosphoenolpyruvate carboxylase activities. 5. Addition of cycloheximide had no effect on the activities of the enzymes after 4h of perfusion at either low or high concentrations of glucose or at high lactate concentration. Cycloheximide also prevented the loss or induction of pyruvate carboxylase and phosphoenolpyruvate carboxylase activities with high substrate concentrations. 6. Significant amounts of glycogen were deposited in all perfusions, except for those containing cycloheximide at the lowest glucose concentration. Lipid was found to increase only in the experiments with high fructose concentrations. 7. Perfusion with either fructose or glucose decreased the rates of ureogenesis; addition of cycloheximide increased urea efflux from the liver.
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PMID:Induction and suppression of the key enzymes of glycolysis and gluconeogenesis in isolated perfused rat liver in response to glucose, fructose and lactate. 435 83

Glucagon (0.04-0.09 mg/kg/min) was given intravenously for either 2 or 3 min to eight patients with fasting-induced hypoglycemia. One child had hepatic phosphorylase deficiency, two children had glucose-6-phosphatase deficiency, two children had debrancher enzyme (amylo-1,6-glucosidase) deficiency, and two children and one adult had decreased hepatic fructose-1,6-diphosphatase (FDPase) activity. Liver biopsy specimens were obtained before and immediately after the glucagon infusion. The glucagon caused a significant increase in the activity of FDPase (from 50+/-10.0 to 72+/-11.7 nmol/mg protein/min) and a significant decrease in the activities of phosphofructokinase (PFK) (from 92+/-6.1 to 41+/-8.1 nmol/mg protein/min) and pyruvate kinase (PK) (from 309+/-39.4 to 165+/-23.9 nmol/mg protein/min). The glucagon infusion also caused a significant increase in hepatic cyclic AMP concentrations (from 41+/-2.6 to 233+/-35.6 pmol/mg protein). Two patients with debrancher enzyme deficiency who had biopsy specimens taken 5 min after the glucagon infusion had persistence of enzyme and cyclic AMP changes for at least 5 min. One child with glucose-6-phosphatase deficiency was given intravenous glucose (150 mg/kg/min) for a period of 5 min after the glucagon infusion and biopsy. The plasma insulin concentration increased from 8 to 152 muU/ml and blood glucose increased from 72 to 204 mg/100 ml. A third liver biopsy specimen was obtained immediately after the glucose infusion and showed that the glucagon-induced effects on PFK and FDPase were completely reversed. The glucagon infusion caused an increase in hepatic cyclic AMP concentration from 38 to 431 pmol/mg protein but the glucose infusion caused only a slight decrease in hepatic cyclic AMP concentration (from 431 to 384 pmol/mg protein), which did not appear to be sufficient to account for the changes in enzyme activities. Hepatic glucose-6-phosphatase and fructose-1,6-diphosphate aldolase activities were not altered by either the glucagon or the glucose infusion in any patients. Cyclic AMP (0.05 mmol/kg) was injected into the portal vein of adult rats and caused enzyme changes similar to those seen with glucagon administration in humans. Our findings suggest that rapid changes in the activities of PFK, PK, and FDPase are important in the regulation of hepatic glycolysis and gluconeogenesis, respectively, in humans and that cyclic AMP may mediate the glucagon- but probably not the glucose-insulin-induced changes in enzyme activities.
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PMID:The rapid changes of hepatic glycolytic enzymes and fructose-1,6-diphosphatase activities after intravenous glucagon in humans. 435 16

Metabolic alterations in ventromedial hypothalamus (VMH)-lesioned rats were investigated by examining daily changes of enzyme activities and urea concentrations three weeks after the operation. VMH-lesions in female adult rats caused a significant elevation in the activity of acetyl-CoA carboxylase in the liver and parametrial adipose tissue. These changes suggest an increased lipogenesis. VMH-lesions also elicited an increase in activities of glucokinase (GK), pyruvate kinase (PK) and fructose 1,6-bisphosphatase (FBPase), and a decrease in activities of phosphofructokinase (PFK), glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) in the liver. The apparently inconsistent changes in activities of key glycolytic enzymes, GK, PK and PFK, and key gluconeogenic enzymes, G6Pase, PEPCK and FBPase in the liver may be explained by the fact that they were favorable for glucose oxidation through pentose phosphate cycle and provide NADPH for lipogenesis in the liver. Furthermore, VMH-lesions induced an increase in urea contents of the liver and serum, and elicited an increase in activity of liver tyrosine aminotransferase (TAT) and a decrease in activity of liver histidase. These changes suggest an accelerated amino acid and protein catabolism, and favor an increment in the supply of the substrate for lipogenesis. Daily rhythms of TAT, histidase activities and serum urea concentration observed in the control rats were abolished by VMH-lesions. These findings suggest that VMH-lesions elicit the loss of these daily rhythms, probably through the disturbance of the circadian rhythm of feeding behavior at this dynamic phase (three weeks after operation) of obesity.
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PMID:Shift of metabolism in rats with ventromedial hypothalamic lesions with respect to changes in daily rhythms of enzyme activity. 614 67

Leishmania mexicana mexicana amastigotes have been shown to contain greater activities than promastigotes of the enzymes that catalyse the beta-oxidation of fatty acids, but lower activities of several glycolytic enzymes, with the activity of pyruvate kinase being especially low. The results suggest the beta-oxidation of fatty acids is relatively more important to Leishmania amastigotes than promastigotes, whereas the reverse is true for glycolysis. Succinic dehydrogenase and peptidase activities were much higher in promastigotes than amastigotes. The activities of glucose-6-phosphatase, fructose-1,6-bisphosphatase, acid phosphatase and glucose-6-phosphate dehydrogenase varied less, although in each case the activity was significantly lower in the mammalian stage. A method for lysing and fractionating L. m. mexicana promastigotes has been developed. Using this procedure it has been established that many of the glycolytic and functionally related enzymes are located in cell organelles, that hexokinase is intimately connected with the particulate part of the parasite, and that the microsomal fraction of L. m. mexicana is very different in composition from the microsomes of mammalian liver cells.
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PMID:A comparative study of Leishmania mexicana amastigotes and promastigotes. Enzyme activities and subcellular locations. 621 17

The hypoglycemia in septic shock due to peritonitis indicates deranged carbohydrate metabolism. To determine if this metabolic failure could be attributed to changes of glucoregulatory enzymes and glycolytic intermediates, activities and changes of these substances in septic shock have been studied in rats. Liver tissue was sampled 5 hours after induction of peritonitis by cecal incision in fasted male rats. Hepatic glycolytic intermediates were assayed by UV-spectrophotometry. Peritonitis caused 33% decrease in glucose-6-phosphate (G6P), a 2.5 fold increase in fructose-1,6-diphosphate (FDP) and a 3.5 fold increase in lactate. Phosphoenolpyruvate (PEP) levels did not show a significant increase in peritonitis. We investigated activities of glucose-6-phosphatase (G6Pase), fructose-1,6-diphosphatase (FDPase), phosphofructokinase ( PFKase ) and pyruvate kinase ( PKase ) in mitochondria-free supernatants from rat liver homogenates. Tissue was sampled 5 hours after induction of peritonitis by cecal incision. Assays were conducted at optimal substrate levels at pH 7.4; NADH charges produced by coupled reactions were determined by UV-spectrophotometry. A significant increase of PFKase and PKase specific activity was observed. These changes were consistent with stimulated glycolysis. For gluconeogenesis to achieve maximum efficiency it would be necessary to inhibit PFKase and PKase completely.
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PMID:[Hepatic glycolytic intermediates and glucoregulatory enzymes in septic shock due to peritonitis: experimental study in rats]. 623 52

The work presented herein describes many of the physiological properties of the phosphofructokinase regulatory factors. Factor activity can be separated into two discrete fractions, which were designated factor A and factor B, based on their respective charges. A preparation containing both factor A and factor B did not protect the following key carbohydrate-metabolizing enzymes from thermal inactivation: glucokinase, glucose-6-phosphatase (solubilized or nonsolubilized forms), pyruvate kinase, glucose-6-P dehydrogenase, muscle-type phosphofructokinase, or the minor liver phosphofructokinase isozyme. Factor activity in this sample was found to be Pronase sensitive, irreversibly precipitated by trichloroacetic acid, reversibly precipitated by adjusting the sample to a pH of 3.0, and stable to heating at 98 degrees C for 20 min. Distribution studies indicated that factor activity was found only in the soluble cell fraction and not in the mitochondrial or nuclear fractions. Factor activity was retained by 12,000-14,000 molecular weight cut-off (MWCO) dialysis tubing, and not retained by 50,000 MWCO dialysis tubing. These studies indicate that fructose-2,6-P2, calmodulin, or insulin-generated mediator are not associated with factor activity. Although fructose-2,6-P2 did not, both factor preparations protect the major liver phosphofructokinase isozyme (liver PFK) from inactivation by lysosomal extracts. In the diabetic rat, the activities of both factors are greatly reduced but return to near normal levels after 48 h of insulin administration. These data suggest that factor B had little or no effect on the kinetic properties of liver PFK. However, factor A was a K-type activator with respect to fructose-6-P, increasing both the Km and Ki for ATP, and slightly increasing the Vm.
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PMID:Properties of the phosphofructokinase regulatory factors. 624 Feb 27

The effects of diabetes on hepatic carbohydrate metabolism were investigated in spontaneously diabetic Bio-Breeding Worcester (BB/W) rats. The juvenile-onset-type syndrome displayed by these animals is characterized by beta-cell destruction with subsequent ketosis-prone insulinopenia. Livers from diabetic animals demonstrated increased adenosine 3',5'-cyclic monophosphate levels but subnormal total protein and glycogen content. Isolated perfused livers of diabetic BB/W rats demonstrated an increased rate of glucose production from [14C]lactate and an impaired rate of glycogen synthesis. These data were consonant with hepatic enzyme studies demonstrating markedly increased activities of component gluconeogenic (glucose-6-phosphatase, fructose-1,6-diphosphatase, phosphoenolpyruvate carboxykinase) and glycogenolytic (glycogen phosphorylase) enzymes with decreased activities of glycolytic (hexokinase, pyruvate kinase) and glycogenic (glycogen synthase) enzymes. These findings agree with previous studies using alloxan- and streptozotocin-induced diabetic animals and suggest that accelerated hepatic gluconeogenesis and impaired glucose utilization are pathognomonic of all insulin-deficient diabetic syndromes.
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PMID:Hepatic carbohydrate metabolism in the spontaneously diabetic Bio-Breeding Worcester rat. 625 45

The variations in enzyme activities involved in the main pathways of liver energetic metabolism--glycolysis, Krebs cycle, gluconeogenesis and lipogenesis--have been studied in rats ranging between the age of 4 days and 21 months. The major changes observed are the following: (1) enzymes involved in glycolysis (pyruvate kinase) and lipogenesis (NADP-malic enzyme, ATP-citrate lyase) decrease in activity during ageing, and (2) gluconeogenic enzymes (phosphoenolpyruvate carboxykinase, glucose-6-phosphatase) are maintained or slightly increased over the same period. The results suggest that an increase in the capacity for gluconeogenesis with respect to that for lipogenesis takes place in the aged rat liver.
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PMID:Metabolic implications of ageing: changes in activities of key lipogenic and gluconeogenic enzymes in the aged rat liver. 626 5


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