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:6.4.1.1 (pyruvate carboxylase)
1,516 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The occurrence and levels of activity of various enzymes of carbohydrate catabolism in culture forms (promastigotes) of 4 human species of Leishmania (L. brasiliensis, L. donovani, L. mexicana, and L. tropica) were compared. These organisms possess enzymes of the Embden-Meyerhof pathway but lack lactate dehydrogenase. No evidence could be found for the production of lactic acid by growing cultures and lactic acid could not be detected either in cell-free preparations or after incubation of cell-free extracts with pyruvate and NADH under appropriate conditions. All 4 species possess alpha-glycerophosphate dehydrogenase and alpha-glycerophosphate phosphatase which together could regenerate NAD, thus compensating for the absence of lactate dehydrogenase. The oxidative and nonoxidative reactions of the hexose monophosphate pathway are present in all 4 species. Cell-free extracts have pyruvate dehydrogenase activity which allows the entry of pyruvate into and its subsequent oxidation through the tricarboxylic acid cycle. All enzymes of this cycle, including a thiamine pyrophosphate dependent alpha-ketoglutarate dehydrogenase, are present. Both NAD and NADP-linked malate dehydrogenase activities are present. The isocitrate dehydrogenase is NADP specific. There is an active glutamate dehydrogenase which could compete with alpha-ketoglutarate dehydrogenase for the common substrate (alpha-ketoglutarate). Replenishment of C4 acids is accomplished by heterotrophic CO2 fixation catalyzed by pyruvate carboxylase. All 4 species have high levels of NADH oxidase activity. Several enzymes thus far not found in any species of Leishmania have been demonstrated. These are: phosphoglucose isomerase, triose phosphate isomerase, fructose-1, 6-diphosphatase, 3-phosphoglycerate kinase, enolase, alpha-glycerophosphate dehydrogenase, alpha-glycerophosphate phosphatase, pyruvate dehydrogenase complex, citrate synthase, aconitase, alpha-ketoglutarate dehydrogenase, glutamate dehydrogenase, and NADH oxidase.
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PMID:Enzymes of carbohydrate metabolism in four human species of Leishmania: a comparative survey. 100 46

Fat-cells were prepared from rat and guinea-pig epididymal adipose tissue and compared on the basis of the intracellular distributions and activities of enzymes and with respect to their utilization of various U-(14)C-labelled substrates for lipogenesis. 1. Compared with the rat, guinea-pig extramitochondrial enzyme activities differed in that aconitate hydratase, alanine aminotransferase, ATP-citrate lyase, lactate dehydrogenase, NAD-malate dehydrogenase, NADP-malate dehydrogenase and phosphoenolpyruvate carboxykinase activities were appreciably lower, whereas aspartate aminotransferase, glucose 6-phosphate dehydrogenase, NADP-isocitrate dehydrogenase and 6-phosphogluconate dehydrogenase activities were appreciably higher. Mitochondrial activities of citrate synthase, NADP-isocitrate dehydrogenase and pyruvate carboxylase were appreciably lower, whereas mitochondrial activities of aspartate aminotransferase, glutamate dehydrogenase, NAD-malate dehydrogenase and phosphoenolpyruvate carboxykinase were higher in the guinea pig compared with the rat. 2. In general guinea-pig fat-cells incorporated acetate and lactate into fatty acids more readily than rat fat-cells, whereas rat fat-cells incorporated glucose and pyruvate more readily than guinea-pig fat-cells. 3. Acetate stimulated the incorporation of glucose into fatty acids in rat fat-cells, but had no appreciable effect upon this process in guinea-pig fat-cells. Acetate greatly decreased the incorporation of lactate into fatty acids in cells from both species. 4. Lactate/pyruvate ratios produced by incubation of guinea-pig cells with glucose+insulin were very low compared with those found with rat cells under the same conditions. 5. With glucose (+insulin) or with glucose+acetate (+insulin) as substrates guinea-pig cells produced enough NADPH by the hexose monophosphate pathway to satisfy the NADPH requirements of lipogenesis. In rat fat-cells under the same conditions, hexose monophosphate-pathway NADPH provision was not sufficient to meet the requirements of lipogenesis. 6. These results are discussed, particularly in relationship to the disposition of cytosolic reducing equivalents in the cells.
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PMID:Lipogenesis in rat and guinea-pig isolated epididymal fat-cells. 415 67

Prolonged exercise increased the concentrations of the hexose phosphates and phosphoenolpyruvate and depressed those of fructose 1,6-bisphosphate, triose phosphates and pyruvate in the liver of the rat. Since exercise increases gluconeogenic flux, these changes in metabolite concentrations suggest that metabolic control is exerted, at least, at the fructose 6-phosphate/fructose 1,6-bisphosphate and phosphoenolpyruvate/pyruvate substrate cycles. Exercise increased the maximal activities of glucose 6-phosphatase, fructose 1,6-bisphosphatase, pyruvate kinase and pyruvate carboxylase in the liver, but there were no changes in those of glucokinase, 6-phosphofructokinase and phosphoenolpyruvate carboxykinase. Exercise changed the concentrations of several allosteric effectors of the glycolytic or gluconeogenic enzymes in liver; the concentrations of acetyl-CoA, ADP and AMP were increased, whereas those of ATP, fructose 1,6-bisphosphate and fructose 2,6-bisphosphate were decreased. The effect of exercise on the phosphorylation-dephosphorylation state of pyruvate kinase was investigated by measuring the activities under conditions of saturating and subsaturating concentrations of substrate. The submaximal activity of pyruvate kinase (0.5 mM-phosphoenolpyruvate), expressed as percentage of Vmax., decreased in the exercised animals to less than half that found in the controls. These changes suggest that hepatic pyruvate kinase is less active during exercise, possibly owing to phosphorylation of the enzyme, and this may play a role in increasing the rate of gluconeogenesis.
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PMID:Metabolic control of hepatic gluconeogenesis during exercise. 622 82

A method for the isolation of Leishmania donovani amastigotes from infected hamster spleen and liver tissues is described. Over 85% of the isolated amastigotes were viable as judged by acridine orange-ethidium bromide staining and in vitro transformation to the promastigote form. A comprehensive survey of the enzymes of carbohydrate metabolism in L. donovani amastigotes and promastigotes was conducted. Amastigotes and promastigotes possess all of the enzymes of the Embden-Meyerhof pathway, hexose monophosphate shunt, and tricarboxylic acid cycle. Cell-free extracts of both forms demonstrate an active glutamate dehydrogenase, thus linking activity which permits entry of pyruvate into the tricarboxylic acid cycle. Both forms demonstrate an active glutamate dehydrogenase, thus linking amino acid metabolism with carbohydrate metabolism. Pyruvate carboxylase, the enzyme responsible for replenishment of C4 acids by heterotrophic CO2 fixation into pyruvate, was also demonstrable in the tissue and insect forms. In general, activities of promastigote enzymes are higher than the amastigote enzymes. Differences between the vertebrate (amastigote) and invertebrate (promastigote) forms in their potential to utilize carbohydrates as substrates would appear to be quantitative rather than qualitative.
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PMID:Enzymes of carbohydrate metabolism in Leishmania donovani amastigotes. 673 17

We reported previously that chronic administration of hydrocortisone to normal developing mice increases the brain glucose content and cerebral energy reserve. The present report concerns possible mechanisms of this action. Increases in brain glucose (and glycogen) levels were not due to reduction of cerebral metabolic rate, and the effect of hydrocortisone in facilitating transport of hexose from blood to brain was not impressive. Chronic hydrocortisone treatment induced increases in the activities of brain glycerophosphate dehydrogenase and pyruvate carboxylase in vivo; there was no effect on eleven other enzymes of brain glucose and glycogen metabolism. In normal nursing mice, hydrocortisone produced consistent elevations in plasma beta-hydroxybutyrate (and glycerol) levels. Brain beta-hydroxybutyrate levels were also increased. Therefore, the brain glucose concentration may be elevated in these animals because of the availability of an increased supply of ketone bodies as alternative substrates for cerebral oxidative metabolism and biosynthesis. Ketonemia, elevated cerebral glucose and beta-hydroxybutyrate concentrations, and increased glycerophosphate dehydrogenase activity in brain suggest possible explanations for the beneficial action of adrenocorticotropic hormone and glucocorticoids in the treatment of infantile myoclonic epilepsy and other neurological disorders.
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PMID:Mechanisms of increased brain glucose and glycogen after hydrocortisone: possible clinical significance. 677 72

Growth efficiency and regulation of key enzyme activities were studied in carbon- and energy-limited chemostat cultures of Saccharomyces cerevisiae grown on mixtures of glucose and ethanol at a fixed dilution rate. Biomass yields on substrate carbon and oxygen could be adequately described as the net result of growth on the single substrates. Activities of isocitrate lyase and malate synthase were not detected in cell-free extracts of glucose-limited cultures. However, both enzymes were present when the ethanol fraction in the reservoir medium exceeded the theoretical minimum above which the glyoxylate cycle is required for anabolic reactions. Fructose-1,6-bisphosphatase activity was only detectable at high ethanol fractions in the feed, when activity of this enzyme was required for synthesis of hexose phosphates. Phospho-enol-pyruvate-carboxykinase activity was not detectable in extracts from glucose-grown cultures and increased with the ethanol fraction in the feed. It is concluded that, during carbon-limited growth of S. cerevisiae on mixtures of glucose and ethanol, biosynthetic intermediates with three or more carbon atoms are preferentially synthesized from glucose. Synthesis of the key enzymes of gluconeogenesis and the glyoxylate cycle is adapted to the cells' requirement for these intermediates. The gluconeogenic enzymes and their physiological antagonists (pyruvate kinase, pyruvate carboxylase and phosphofructokinase) were expressed simultaneously at high ethanol fractions in the feed. If futile cycling is prevented under these conditions, this is not primarily achieved by tight control of enzyme synthesis.
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PMID:Regulation of carbon metabolism in chemostat cultures of Saccharomyces cerevisiae grown on mixtures of glucose and ethanol. 759 44

A mathematical model of mammalian cell intermediary metabolism is presented. It describes the distribution of the carbon-13 isotope (13C) at the different carbon positions of metabolites in cells fed with 13C-enriched substrates. The model allows the determination of fluxes through different metabolic pathways from 13C- and 1H-NMR spectroscopy and mass spectrometry data. The considered metabolic network includes glycolysis, gluconeogenesis, the citric acid cycle and a number of reactions corresponding to protein or fatty acid metabolism. The model was used for calculating metabolic fluxes in a rat tumor cell line, the C6 glioma, incubated with [1-13C]glucose. After evolution to metabolic and isotopic steady states, the intracellular metabolites were extracted with perchloric acid. The specific enrichments of glutamate, aspartate and alanine carbons were determined from 13C-, 1H-NMR spectroscopy, or mass spectrometry data. Taking into account the rate of glucose consumption and of lactate formation, determined from the evolution of glucose and lactate contents in the cell medium, and knowing the activity of the hexose monophosphate shunt, it was possible to estimate the absolute values of all the considered fluxes. From the analysis the following results were obtained. (a) Glucose accounts for about 78% of the pyruvate and 57% of the CoASAc. (b) A metabolic channelling occurs at the citric acid cycle level; it favours the conversion of carbons 2, 3, 4, and 5 of 2-oxoglutarate into carbons 1, 2, 3, and 4 of oxaloacetate, respectively. The percentage of channelled metabolites amounts to 39%. (c) The pyruvate carboxylase activity and the efflux from the citric acid cycle are estimated to be very low, suggesting a lack of glutamine production in C6 cells. The results emphasize different metabolic characteristics of C6 cells when compared to astrocytes, their normal counterpart.
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PMID:Metabolic flux determination in C6 glioma cells using carbon-13 distribution upon [1-13C]glucose incubation. 790 Oct 7

The metabolism of [1-13C]glucose in rat cerebellum astrocytes and granule cells was investigated using 13C- and 1H-NMR spectroscopy. Near homogeneous primary cultures of each cell type were incubated with [1-13C]glucose, under the same conditions. Analysing the relative 13C enrichments of metabolites in spectra of cell perchloric acid extracts, on the one hand, the 13C-1H spin-coupling patterns in 1H-NMR spectra of cell medium lactate and the 13C-13C spin-coupling patterns in 13C-NMR spectra of purified cell glutamate, on the other hand, showed significant differences, between the two cell types, in the activity of various metabolic ways. First, the carbon flux through the oxidative branch of the hexose monophosphate shunt, which leads to unenriched lactate, was found higher in granule cells than in astrocytes. Second, although the specific 13C enrichment of lactate was higher in astrocytes than in granule cells, the fraction of 13C-enriched acetyl-CoA entering the citric acid cycle was more than twice as high in granule cells as in astrocytes. Lactate C3 and acetyl-CoA C2 enrichments were very similar in granule cells, whereas acetyl-CoA C2 enrichment was 60% lower than that of lactate C3 in astrocytes. These results can be explained by the fact that granule cells used almost exclusively the exogenous glucose to fuel the citric acid cycle, whereas astrocytes used concomitantly glucose and other carbon sources. Last, in the case of granule cells, glutamate C2 and C3 enrichments were equivalent; the carbon flux through the pyruvate carboxylase route was evaluated to be around 15% of the carbon flux through the citrate synthetase route. In astrocytes, glutamate C2 enrichment was higher than that of C3, which could be explained by a pyruvate carboxylase activity much more active in these cells than in granule cells.
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PMID:[1-13C]glucose metabolism in rat cerebellar granule cells and astrocytes in primary culture. Evaluation of flux parameters by 13C- and 1H-NMR spectroscopy. 790 Oct 11

The fate of [3-13C]alanine administered to last instar larvae of an insect Manduca sexta was investigated in vivo by 13C-NMR spectroscopy. Following injection of the isotopically substituted substrate and conversion to [3-13C]pyruvate 13C was principally incorporated into C2, C3 and C4 of glutamate and glutamine in unparasitized ad libitum-fed larvae, insects starved 48 hr prior to injection and larvae parasitized by the insect parasite Cotesia congregata. Selective labeling at C2 and C3 of glutamate/glutamine resulted from carboxylation of [3-13C]pyruvate to [2,3-13C]oxaloacetate catalyzed by pyruvate carboxylase, randomization of the label in fumarate, and synthesis of glutamate and glutamine after condensation with acetyl CoA to [2 proR,3-13C]citrate. In contrast, enrichment at C4 of glutamate and glutamine resulted from oxidation [3-13C]pyruvate to [2-13C]acetyl CoA catalyzed by pyruvate dehydrogenase followed by condensation with oxaloacetate. The ratio of enrichment (C2 + C3): C4 provided a measure of the relative contributions of the pyruvate dehydrogenase and pyruvate carboxylase catalyzed pathways of substrate utilization by the tricarboxylic acid cycle. The mean ratio was 0.6 and 0.7 in control and parasitized larvae, respectively, and 2.4 in starved insects. The latter result demonstrated that substrate utilization by the TCA cycle was markedly altered by starvation. In addition, the rate of labeled alanine metabolism was significantly reduced by starvation. The concentrations of glutamate and glutamine in the blood (hemolymph) were similar in all three groups of insects. No evidence for gluconeogenesis was observed in any group. Starved larvae incorporated label into C6 of glucose and trehalose but no complementary enrichment at C1 was observed. This result was consistent with the activity of the non-oxidative phase of the pentose phosphate pathway during which labeled glyceraldehyde-3-phosphate arising from [3-13C]alanine reacts with sedoheptulose-7-phosphate yielding erythrose-4-phosphate and [6-13C]fructose-6-phosphate catalyzed by transaldolase. Specifically labeled fructose-6-phosphate then gives rise to glucose and trehalose labeled at C6. Preliminary analysis of the hemolymph of starved insects indicated the presence of several hexose phosphates labeled at C6. The hemolymph level of trehalose was significantly reduced in both starved and parasitized insects. Lipogenesis from [3-13C]alanine was evident in unparasitized control larvae but was absent in parasitized and starved insects. The pattern of labeling in fatty acid was consistent with de novo pathway utilizing [2-13C]acetyl CoA derived by oxidation of [3-13C]alanine.
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PMID:Metabolic fate of alanine in an insect Manduca sexta: effects of starvation and parasitism. 810 Jul 13

(1) Liver cells from starved rats were incubated with 10 mM L-lactate, 1 mM pyruvate and 0.3 microM glucagon in the presence and absence of the mild respiratory inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) at 0.5 mM. (2) The whole cell concentrations of phosphoenolpyruvate, 2-phosphoglycerate and 3-phosphoglycerate increased about 2-fold, whilst the triose and hexose phosphate concentrations all decreased significantly. Similar results were obtained with 0.15 microM oligomycin and 10 microM atractyloside. (3) These data can be explained by a substantial decrease in the cytosolic free concentration ratio of ATP/ADP acting on the equilibrium of glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase. (4) The increase in cytosolic phosphoenolpyruvate concentration can account for the observed increase in pyruvate kinase flux that occurs under these conditions (Pryor et al. (1987) Biochem. J. 247, 449-457). (5) An inhibition of pyruvate carboxylase was also implied by a decrease in calculated tissue oxaloacetate concentrations, confirming a role for both enzymes in the inhibition of gluconeogenesis. (6) Whole cell concentrations of effectors of pyruvate carboxylase activity were measured; only the ATP/ADP ratio decreased significantly. (7) Subcellular fractionation studies showed a good correlation between the measured mitochondrial ATP/ADP ratio and rates of gluconeogenesis both in the presence and absence of oleate. (8) A similar correlation could be observed between rates of pyruvate carboxylation and the measured matrix ATP/ADP ratio in isolated liver mitochondria from starved rats. (9) Data are also presented suggesting an additional effect of DCMU on the rate pyruvate carboxylation in situ under some circumstances, mediated by decreases in mitochondrial acetyl-CoA and cytosolic pyruvate concentrations. (10) It is noted that the effects of phenylethylbiguanide (phenformin) on the rate of gluconeogenesis and metabolite profiles in the perfused liver (Cooke et al. (1973) J. Biol. Chem. 248, 5272-5277) are similar to those caused by DCMU, supporting a mitochondrial locus of action for this hypoglycaemic agent.
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PMID:The mechanisms by which mild respiratory chain inhibitors inhibit hepatic gluconeogenesis. 845 80


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