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:4.1.1.32 (phosphoenolpyruvate carboxykinase)
4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of postpartum supplementation with rumen undegradable protein on the activities of gluconeogenic enzymes was studied in cows with induced fatty liver. Prepartum liver and blood samples were collected at about one week before the expected date of calving and postpartum samples were collected at 10 and 20 days (d) postpartum. At 10 d postpartum, concentrations of serum nonesterified fatty acids and hepatic triacylglycerol levels were higher than at one wk before parturition. The postpartum increases in nonesterified fatty acids and hepatic triacylglycerols were significantly higher in the cows that were fed extra protein than in the control cows. There were no differences between the groups with regard to postpartum changes in the concentrations of plasma glucose, liver glycogen, and serum insulin. The postpartum increase in the activity of fructose 1-6-bisphosphatase was higher in the test group than in the control group, but the increase in the activity of glucose-6-phosphatase was lower. There were no group differences in the postpartum activities of phosphoenolpyruvate carboxykinase, pyruvate carboxylase, and propionyl-CoA carboxylase. Our results suggest that intense lipolysis released more glycerol in the protein-supplemented cows, which stimulated the activity of fructose 1-6-bisphosphatase. However, postpartum rumen undegradable protein supplementation did not affect the activities of the other enzymes of gluconeogenesis, and fatty liver was even exacerbated.
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PMID:The effect of postpartum rumen undegradable protein supplementation on hepatic gluconeogenic enzyme activities in dairy cows with fatty liver. 1246 10

Brown adipose tissue (BAT) glyceroneogenesis was evaluated in rats either fasted for 48 h or with streptozotocin-diabetes induced 3 days previously or adapted for 20 days to a high-protein, carbohydrate-free (HP) diet, conditions in which BAT glucose utilization is reduced. The three treatments induced an increase in BAT glyceroneogenic activity, evidenced by increased rates of incorporation of [1-14C]pyruvate into triacylglycerol (TAG)-glycerol in vitro and a marked, threefold increase in the activity of BAT phosphoenolpyruvate carboxykinase (PEPCK). BAT glycerokinase activity was not significantly affected by fasting or diabetes. After unilateral BAT denervation of rats fed either the HP or a balanced diet, glyceroneogenesis activity increased in denervated pads, evidenced by increased rates of nonglucose carbon incorporation into TAG-glycerol in vivo (difference between 3H2O and [14C]glucose incorporations) and of [1-14C]pyruvate in vitro. PEPCK activity was not significantly affected by denervation. The data suggest that BAT glyceroneogenesis is not under sympathetic control but is sensitive to hormonal/metabolic factors. In situations of reduced glucose use there is an increase in BAT glyceroneogenesis that may compensate the decreased generation of glycerol-3-phosphate from the hexose.
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PMID:Control of glyceroneogenic activity in rat brown adipose tissue. 1279 97

It has been observed previously that hormone-sensitive lipase-deficient (HSL-ko) mice have reduced white adipose tissue (WAT) stores compared to control mice. These findings contradict the expectation that the decreased lipolytic activity in WAT of HSL-ko mice would cause accumulation of triglycerides (TGs) in that tissue. Here we demonstrate that the cellular TG synthesis in HSL-deficient WAT is markedly reduced due to downregulation of the enzymatic activities of glycerophosphate acyltransferase, dihydroxyacetonphosphate acyltransferase, lysophosphatidate acyltransferase, and diacylglycerol acyltransferase. Fatty acid de novo synthesis is also decreased due to reduced cellular glucose uptake, reduced glucose incorporation into adipose tissue lipids, and reduced activities of acetyl:CoA carboxylase and fatty acid synthase. Finally, the activities of phosphoenolpyruvate carboxykinase (PEPCK), acyl:CoA synthetase (ACS), and glucose 6-phosphate dehydrogenase, the enzymes that provide glycerol-3-phosphate, acyl-CoA, and NADPH for TG synthesis, respectively, are decreased in HSL-ko mice. The reduced expression of the peroxisome proliferator-activated receptor gamma (PPAR gamma) target genes PEPCK, ACS, and aP2, as well as reduced mRNA levels of PPAR gamma itself, suggest the involvement of this transcription factor in the downregulation of lipogenesis. Taken together, these results establish that in the absence of HSL, the reduced NEFA production is counteracted by a drastic reduction of NEFA reesterification that provides sufficient quantities of NEFA for release into the circulation. These metabolic adaptations result in decreased fat mass in HSL-ko mice.
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PMID:Decreased fatty acid esterification compensates for the reduced lipolytic activity in hormone-sensitive lipase-deficient white adipose tissue. 1292 28

The gluconeogenic phosphoenolpyruvate (PEP) carboxykinase is active in Escherichia coli during its growth on glucose. The present study investigated the influence of growth rates and PEP carboxykinase knockout on the anaplerotic fluxes in E. coli. The intracellular fluxes were determined using the complementary methods of flux ratio analysis and metabolic flux analysis based on [U-(13)C(6)]glucose labeling experiments and 2D nuclear magnetic resonance (NMR) spectroscopy of cellular amino acids and glycerol. Significant activity of PEP carboxykinase was identified in wild-type E. coli, and the ATP dissipation for the futile cycling via this reaction accounted for up to 8.2% of the total energy flux. Flux analysis of pck deletion mutant revealed that abolishment of PEP carboxykinase activity resulted in a remarkably reduced flux through the anaplerotic PEP carboxylase and the activation of the glyoxylate shunt, with 23% of isocitrate found being channeled in the glyoxylate shunt. The changes in intracellular metabolite concentrations and specific enzyme activities associated with different growth rates and pck deletion, were also determined. Combining the measurement data of in vivo fluxes, metabolite concentrations and enzyme activities, the in vivo regulations of PEP carboxykinase flux, PEP carboxylation, and glyoxylate shunt in E. coli are discussed.
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PMID:Analysis of Escherichia coli anaplerotic metabolism and its regulation mechanisms from the metabolic responses to altered dilution rates and phosphoenolpyruvate carboxykinase knockout. 1296 69

Theodore, Theodore S. (University of Pittsburgh, Pittsburgh, Pa.), and Ellis Englesberg. Mutant of Salmonella typhimurium deficient in the carbon dioxide-fixing enzyme phosphoenolpyruvic carboxylase. J. Bacteriol. 88:946-955. 1964.-Resting cells of Salmonella typhimurium wild type (C(+)dg(s)) and the C(-)dg(s) mutant characterized by impaired glucose and glycerol metabolism are able to oxidize Krebs cycle intermediates to the same extent. The wild type oxidized glucose and pyruvate "completely," and the mutant oxidized these substrates at a reduced rate and incompletely, with the accumulation of acetate. Resting cells of the wild type in the presence of NaHCO(3)-C(14) and glucose incorporated 11 times more CO(2) than did similar suspensions of the mutant. Extracts prepared from cells previously grown in a mineral glucose supplemented medium revealed that the mutant was deficient in the CO(2)-fixing enzyme phosphoenolpyruvic carboxylase (PEP carboxylase). This enzyme was found to be present in the wild-type extracts. It catalyzes the formation of oxaloacetate from phosphoenolpyruvate and CO(2) in the presence of Mn(++) or Mg(++). No added nucleotides are required for its activity. Since only low levels of phosphoenolpyruvic carboxykinase activity are present in extracts prepared from both kinds of cells grown in a mineral glucose supplemented medium, and perhaps only trace amounts of the malic enzyme, phosphoenolpyruvic carboxytransphosphorylase, and of the enzyme requiring pyruvate, CO(2), and adenosine triphosphate are present, it was concluded that PEP carboxylase is required for CO(2), fixation in this organism. The loss of this enzyme prevents the growth of the mutant in a mineral-glucose or mineral-glycerol medium, and results in the incomplete oxidation of glucose and pyruvate with the accumulation of acetate. This is the first demonstration of the essential role of this particular enzyme in CO(2) fixation in chemoorganotrophs.
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PMID:MUTANT OF SALMONELLA TYPHIMURIUM DEFICIENT IN THE CARBON DIOXIDE-FIXING ENZYME PHOSPHOENOLPYRUVIC CARBOXYLASE. 1421 58

We studied in rats the expression of genes involved in gluconeogenesis from glutamine and glycerol in the small intestine (SI) during fasting and diabetes. From Northern blot and enzymatic studies, we report that only phosphoenolpyruvate carboxykinase (PEPCK) activity is induced at 24 h of fasting, whereas glucose-6-phosphatase (G-6-Pase) activity is induced only from 48 h. Both genes then plateau, whereas glutaminase and glycerokinase strikingly rebound between 48 and 72 h. The two latter genes are fully expressed in streptozotocin-diabetic rats. From arteriovenous balance and isotopic techniques, we show that the SI does not release glucose at 24 h of fasting and that SI gluconeogenesis contributes to 35% of total glucose production in 72-h-fasted rats. The new findings are that 1) the SI can quantitatively account for up to one-third of glucose production in prolonged fasting; 2) the induction of PEPCK is not sufficient by itself to trigger SI gluconeogenesis; 3) G-6-Pase likely plays a crucial role in this process; and 4) glutaminase and glycerokinase may play a key potentiating role in the latest times of fasting and in diabetes.
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PMID:Induction of control genes in intestinal gluconeogenesis is sequential during fasting and maximal in diabetes. 1455 23

FA (fatty acid) recycling in adipose tissue appears to be an important pathway for regulating FA release into the blood during fasting. Re-esterification requires G3P (glycerol 3-phosphate), which cannot be synthesized from glucose because glycolysis is much reduced under such circumstances. In addition, G3P can scarcely originate from glycerol since glycerol kinase has a very low activity in white adipose tissue. It was shown about 35 years ago that a metabolic pathway named glyceroneogenesis, which allows G3P synthesis from non-carbohydrate precursors like pyruvate, lactate or amino acids, is activated during fasting. The major enzyme in this pathway was shown to be PEPCK-C [cytosolic phosphoenolpyruvate carboxykinase (GTP); EC 4.1.1.32]. The present review analyses the mechanisms by which a series of hormones and nutrients affect PEPCK-C gene transcription and glyceroneogenesis and describes evidence for dysregulation of this pathway in type 2 diabetes.
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PMID:Fatty acid recycling in adipocytes: a role for glyceroneogenesis and phosphoenolpyruvate carboxykinase. 1464 Oct 9

The effect of gene knockout on metabolism in the pflA-, pflB-, pflC-, and pflD- mutants of Escherichia coli was investigated. Batch cultivations of the pfl- mutants and their parent strain were conducted using glucose as a carbon source. It was found that pflA- and pflB- mutants, but not pflC- and pflD- mutants, produced large amounts of D-lactate from glucose under the microaerobic condition, and the maximum yield was 73%. In order to investigate the metabolic regulation mechanism, we measured enzyme activities for the following eight enzymes: glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), pyruvate kinase, lactate dehydrogenase (LDH), phosphoenolpyruvate carboxylase, acetate kinase, and alcohol dehydrogenase. Intracellular metabolite concentrations of glucose 6-phosphate, fructose 1,6-bisphosphate, phosphoenolpyruvate, pyruvate, acetyl coenzyme A as well as ATP, ADP, AMP, NADH, and NAD+ were also measured. It was shown that the GAPDH and LDH activities were considerably higher in pflA- and pflB- mutants, which implies coupling between NADH production and consumption between the two corresponding reactions. The urgent energy requirement was shown by the lower ATP/AMP level due to both oxygen limitation and pfl gene knockout, which promoted significant stepping-up of glycolysis when using glucose as a carbon source. It was shown that the demand for energy is more important than intracellular redox balance, thus excess NADH produced through GAPDH resulted in a significantly higher intracellular NADH/NAD+ ratio in pfl- mutants. Consequently, the homolactate production was achieved to meet the requirements of the redox balance and the energy production through glycolysis. The effect of using different carbon sources such as gluconate, pyruvate, fructose, and glycerol was investigated.
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PMID:The effect of pfl gene knockout on the metabolism for optically pure D-lactate production by Escherichia coli. 1467 46

Glyceroneogenesis is the synthesis of 3-glycerol phosphate by an abbreviated version of gluconeogenesis. The research that led to the discovery of glyceroneogenesis in white adipose tissue is presented. This pathway is active during fasting in white and brown adipose tissue and in the liver as part of the triglyceride/fatty acid cycle. Glyceroneogenesis is critical for the extensive recycling of free fatty acid (FFA) back to triglyceride that occurs in mammals, including humans, after lipolysis, when up to 65% of the fatty acids are re-esterified back to triglyceride. The rate-limiting enzyme in this pathway is the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) (4.1.1.32) (PEPCK-C). Transcription of this gene is induced in adipose tissue and liver during fasting. Ablation of expression of the gene for PEPCK-C in white adipose tissue of mice results in lipodsytrophy, while overexpression of the gene for this enzyme in adipose tissue causes obesity. The critical role of glyceroneogenesis in diabetes was suggested by experiments in which the gene for PEPCK-C is induced in white adipose tissue by rosiglitazone, a drug used to control diabetes in humans. This was accompanied by a marked decrease in FFA release from adipose tissue due to an induction in glyceroneogenesis in the tissue. Since the chronic release of FFA by adipose tissue is a critical factor in the development Type 2 diabetes, it is likely that rosiglitazone acts in part by stimulating transcription of the gene for PEPCK-C, thereby increasing rate of glyceroneogenesis and lowering the rate of FFA release from adipose tissue.
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PMID:Glyceroneogenesis revisited. 1473 71

The activities of ribulose-1,5-bisphosphate carboxylase-oxygenase, Rubisco (E.C. 4.1.1.39) and phosphoenolpyruvate carboxylase, PEPc (E.C. 4.1.1.31), and concentrations of protein and chlorophyll were measured in extracts from cotyledons and first leaves of Qualea grandiflora Mart. (Vochysiaceae) seedlings after transfer from high-light (20 days at 320 micro mol m(-2) s(-1), PAR) to low-light (35 days at 120 micro mol m(-2) s(-1), PAR) conditions. When Tween 20 and glycerol were added to the extraction medium, Rubisco activities obtained for Qualea grandiflora were comparable to published values for several coniferous species and the broad-leaved species, Prunus avium L. Stella, grown in a similar light environment. Rubisco activity in cotyledons of Q. grandiflora grown in high light for 20 days and then transferred to low light for a further 35 days was similar to the activity in cotyledons of plants grown continuously in high light. However, the first leaf above the cotyledons showed a greater response to the change in irradiance; in high light, Rubisco activity of the first leaf was 1.8 times higher on a fresh weight basis and 2.7 times higher on an area basis than that of leaves transferred from high to low light. Fresh weight and chlorophyll concentration expressed on a unit leaf area basis were also higher in the high-light treatment. These responses to irradiance are indicative of a species adapted to growth in an unshaded habitat. The PEPc activity in leaves was 15% of Rubisco activity, which is typical of species with a C(3) photosynthetic pathway. The relatively slow growth rate of Q. grandiflora observed in these experiments could not be attributed to a low carboxylation capacity per unit leaf area.
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PMID:Rubisco and PEP carboxylase responses to changing irradiance in a Brazilian Cerrado tree species, Qualea grandiflora Mart. (Vochysiaceae). 1496 11


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