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:4.1.1.49 (phosphoenolpyruvate carboxykinase)
4,654 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Selective glucose-free media have been used to study the reexpression of liver-specific gluconeogenic enzymes in rat hepatoma X mouse lymphoblastoma somatic hybrids. The utilization for gluconeogenesis of dihydroxyacetone or oxaloacetate requires two enzymes: fructose diphosphatase as well as either triokinase for the former or phosphoenolpyruvate carboxykinase for the latter. By sequential selection with these substrates, the reexpression of the three gluconeogenic enzymes has been dissociated. The reexpression of these enzymes is correlated with the loss of mouse chromosomes. In addition, the characterization of the parental forms of aldolase B, another liver-specific enzyme, shows that reexpression corresponds to the simultaneous production of the rat and mouse enzymes. These results demonstrate the chromosomal origin of extinction and suggest that activation of mouse silent genes which accompanies reexpression can occur without loss of the parental determinations. The hypothesis that determination involves regulatory rather than structural genes is discussed.
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PMID:Expression of differentiated functions in hepatoma cell hybrids: selection in glucose-free media of segregated hybrid cells which reexpress gluconeogenic enzymes. 20 53

Previous studies showed that livers from carnivorous birds have a higher gluconeogenic capacity and higher levels of gluconeogenic enzymes than livers from granivorous birds. In this work we compare the effects of fasting and adrenalectomy on gluconeogenesis. Fasting in the chicken elicited increased rates of incorporation of 14C from alanine into blood glucose, increased gluconeogenesis in liver slices, and increased activities of four gluconeogenic enzymes: glucose-6-phosphatase, phosphoenolpyruvate carboxykinase, alanine aminotransferase, and aspartate aminotransferase. These responses in the chicken resemble those observed in fasted rodents. In marked contrast, fasting in black vultures induced decreased rates of incorporation of alanine label into circulating glucose, decreased gluconeogenesis in liver slices, and no change in any of the four enzymes studied. This unusual response to fasting in the carnivorous bird is probably related to the high-protein-low-carbohydrate content of the diet. Fasted adrenalectomized birds (granivorous and carnivorous) had reduced rates of in vivo glucose synthesis, decreased liver gluconeogenesis, and lower activity of glucose-6-phosphatase and aspartate aminotransferase, without change in phosphoenolpyruvate carboxykinase and alanine aminotransferase activities.
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PMID:Fasting, adrenalectomy, and gluconeogenesis in the chicken and a carnivorous bird. 20 1

The activities of pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), and glycogen synthetase (GS) were determined in the cancerous and in the apparently uninvolved (host) regions of livers from primary hepatoma patients as well as in normal adult human livers and human fetal livers. The activities of these enzymes were also assayed in a fairly fast-growing, 3'-methyl-4-dimethylaminoazobenzene-induced transplantable rat hepatoma and in hepatoma cell lines derived from both rat and human tumors. In the human hepatoma, as in the rat hepatoma, the activities of PC, PEPCK, and G6Pase were considerably reduced, compared to those in the host liver. The activities of both the a (glucose 6-phosphate-independent) and b (glucose 6-phosphate-dependent) forms of GS were also lower in human and rat hepatomas than in the respective host livers. Activities of PC, PEPCK, and G6Pase in the human hepatomas were often comparable with those of fetal livers. In rat and human hepatoma cells, the activities of PC, PEPCK, and G6Pase were similar to or lower than the activities in the respective hepatomas; the activities of GS a were also similar to those in the hepatoma, whereas the activities of GS b were somewhat higher.
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PMID:Activities of key gluconeogenic enzymes and glycogen synthase in rat and human livers, hepatomas, and hepatoma cell cultures. 20 62

1. The aim of this work was to discover the steps at which the conversion of oxaloacetate to glucose 6-phosphate during gluconeogenesis is regulated in the cotyledons of 5-day-old seedlings of Cucurbita pepo. 2. We estimated the maximum catalytic activities of all the enzymes in the above sequence and also the amounts of their substrates present in vivo. The results show that the reactions catalysed by fructose-1,6-bisphosphatase and phosphoenolpyruvate carboxykinase are the only ones in the sequence that are substantially displaced from equilibrium in vivo. 3. We also determined the effects of 3-mercaptopicolinic acid, an inhibitor of gluconeogenesis, on the amounts of the gluconeogenic intermediates present in vivo. The results show that the enzyme system, fructose-1,6-bisphosphatase: phosphofructokinase, and the system phosphoenolpyruvate carboxykinase: phosphoenolpyruvate carboxylase make major contributions to the regulation of gluconeogenesis in the cotyledons. 4. Possible mechanisms for the above regulation are discussed.
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PMID:Identification of the regulatory steps in gluconeogenesis in cotyledons of Cucurbita pepo. 20 45

The renal gluconeogenic response to the inhibition of liver gluconeogenesis was studied in rats treated with CCl4. This treatment resulted in a generalized fall of hepatic gluconeogenic enzyme activities and a complete impairment of liver gluconeogenesis. On the contrary, an enhancement of renal phosphoenolpyruvate carboxykinase activity and gluconeogenic ability was found. This stimulation seemed to be not related to metabolic acidosis but mediated by glucocorticoids. On the other hand, the pattern of intermediate metabolites in kidney suggested that renal gluconeogenesis was operative in these conditions, probably playing a key role in glucose homeostasis.
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PMID:Induction of rat kidney gluconeogenic ability after impairment of liver gluconeogenesis. 21 Sep 98

Xenopus laevis (Daudin) adult specimens were submitted to hypophysectomy. Although the operation resulted subtotal, it served the purpose of removing the prolactin-producing cells, whereby the involvement of endogenous prolactin in osmoregulation phenomena was excluded. In the operated animals treated with ovine prolactin the following metabolic parameters, which are closely dependent upon interrenal activity, were estimated: 1) intestine alkaline phosphomonoesterase activity (E.C. 3.1.3.1); 2) liver glycogen level; 3) glucose-6-phosphatase (E.C. 3.1.3.9.) and phosphoenolpyruvate carboxykinase (E.C. 4.1.1.32.) in the liver; 4) blood glucose level; 5) blood ammonia and urea levels; 6) carbamoylphosphate synthetase activity in the liver (E.C. 2.7.2.a); 7) muscle sodium and potassium levels. The above metabolic parameters were found to be pressed by subtotal hypophysectomy and after subsequent prolactin treatment showed the tendency to go back to values similar to those of control animals.
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PMID:Biochemical data on subtotally hypophysectomized Xenopus laevis (Daudin) adult specimens treated or not with prolactin. 21 25

Ammoniagenesis and gluconeogenesis have been studied in foetal rat kidneys during the five last days of gestation by measuring in vitro NH3 and glucose productions from glutamine and by assaying activities of soluble phosphoenolpyruvate carboxykinase(PEPCK) and glucose 6-phosphatase (G6Pase). These studies were carried out in normal (mean blood pH: 7.30) and acidotic (pH: 7.12) foetuses. In normal foetuses, NH3 production by kidney cortex slices remains constant throughout the studied period of development, at a level 10-fold lower than the maternal one. On day 20 of gestation, a low glucose production (20-fold lower than the maternal one) appears for the first time. This may be related to an increase of PEPCK and G6Pase activities which occurs between day 19 and 20. In 20 days old foetuses, NH4Cl induced acidosis stimulates NH3 production but has no effect on PEPCK activity and glucose production. A response of gluconeogenesis to acidosis is observed one day later (day 21).
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PMID:Development of ammonia and glucose productions from glutamine in foetal rat kidney; effects of metabolic acidosis. 21 16

The major effects of glucocorticoids on white fat are shown in Fig. 1. The glucocorticoid diffuses into the cytosol of fat cells where it binds to a soluble receptor. The steroid-receptor complex then enters the nucleus where RNA synthesis is increased. The next step may be a selective increase in synthesis of protein(s). In any event, there is an inhibition of the membrane-bound glucose transport system and an increase in the ability of lipolytic agents to activate triglyceride lipolysis. There is also a decrease in phosphoenolpyruvate carboxykinase, lipoprotein lipase, and fatty acid synthetase that occurs after a somewhat longer lag period than is required for inhibition of glucose transport or lipolysis activation. Whether these effects are independent or secondary to the glucose transport inhibition and lipolysis activation remains to be established.
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PMID:Inhibition of glucose transport in fat cells and activation of lipolysis by glucocorticoids. 22 73

Strains of Saccharomyces cerevisiae bearing nonsense mutations in the structural gene for proteinase B (EC 3.4.22.9) have been examined for the ability to make the transition from growth on acetate to growth on glucose and for the ability to inactivate three glucoeogenic enzymes during the transition because proteinase B has been proposed by others to be responsible for the inactivation of the three enzymes during the growth transition. The mutant strains make the growth transition normally. Catabolite inactivation of hexosediphosphatase (D-fructose-1,6-biphosphate 1-phosphohydrolase, EC 3.1.3.11), malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37), and phosphoenolpyruvate carboxykinase (ATP) [ATP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.49] occurred in prb1 mutants with kinetics similar to those seen in wild-type strains. We infer that proteinase B activity is not essential for the process of catabolite inactivation.
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PMID:Catabolite inactivation of gluconeogenic enzymes in mutants of yeast deficient in proteinase B. 22 2

Hyperinsulinemia was produced in fetal rhesus monkeys for 21 days in the last third of gestation by subcutaneous pork insulin injected at 19 U a day. Plasma insulin concentrations in treated fetuses (N = 4) were 3525 microU/ml. There was no difference in paired pre- and post-treatment fetal plasma glucose concentration. Activity of the hepatic enzymes that promote glucose utilization (glucokinase and hexokinase) and glycolysis (phosphofructokinase, pyruvate kinase, and pyruvate dehydrogenase) was unaffected. Similarly, glycogen metabolism enzymes (active and inactive synthase and phosphorylase) were unaltered. Two gluconeogenic enzymes (PEPCK and glucose-6-phosphatase) were diminished in the treated group compared with controls. Fetal hyperinsulinemia enhanced lipogenic and NADPH-producing enzyme activities, as evidenced by a twofold increase in fatty acid synthase and in citrate cleavage enzyme activity. Malic enzyme was absent. Hyperinsulinemia with euglycemia (1) increases the activity of enzymes that participate in lipogenesis, (2) decreases some of those controlling gluconeogenesis, and (3) has no effect on the enzymes of glycolysis.
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PMID:Chronic hyperinsulinemia in the fetal rhesus monkey: effects on hepatic enzymes active in lipogenesis and carbohydrate metabolism. 22 50


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