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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)

1. The activities of some enzymes involved in both the utilization of glucose (pyruvate kinase, ATP citrate lyase, NADP-specific malate dehydrogenase, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and NADP-specific isocitrate dehydrogenase, all present in the supernatant fraction of liver homogenates) and the formation of glucose by gluconeogenesis (glucose 6-phosphatase in the whole homogenate and fructose 1,6-diphosphatase, phosphopyruvate carboxylase, NAD-specific malate dehydrogenase and fumarase in the supernatant fraction) have been determined in rat liver around birth and in the postnatal period until the end of weaning. 2. The activities of those enzymes involved in the conversion of glucose into lipid are low during the neonatal period and increase with weaning. NADP-specific malate dehydrogenase first appears and develops at the beginning of the weaning period. 3. The marked increase in cytoplasmic phosphopyruvate carboxylase activity at birth is probably the major factor initiating gluconeogenesis at that time. 4. The results are discussed against the known changes in dietary supplies and the known metabolic patterns during the period of development.
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PMID:Changes in activity of some enzymes involved in glucose utilization and formation in developing rat liver. 438 35

1. Foetal rat liver slices incorporate the C-3 of aspartate and C-2 of glutamate into fatty acids at rates equal to those observed with adult rat liver slices. Incorporation of either of these labelled carbon atoms into fatty acids would require a functioning citrate-cleavage pathway which consists of the enzymes ATP-citrate lyase, NAD-malate dehydrogenase and NADP-malate dehydrogenase. However, NADP-malate dehydrogenase is present in foetal rat liver at only 5% of the activity detectable in adult rat liver. 2. From these findings and the effect of cofactors on the formation of (14)CO(2) from [1,5-(14)C(2)]citrate in liver supernatant fractions (100000g), it is suggested that NADP-malate dehydrogenase limits the citrate-cleavage sequence. 3. Measurement of the citrate-cleavage pathway by incorporation studies with [3-(14)C]aspartate and [U-(14)C]glucose and by determining the activities of ATP-citrate lyase and NADP-malate dehydrogenase have shown that this sequence of reactions is present in the liver of the bovine foetus but not in the adult. However, C-2 of glutamate is not incorporated into fatty acids or non-saponifiable lipid by bovine liver slices. This finding as well as those presented above for the adult and foetal rat liver are interpreted on the basis of a competition between phosphoenolpyruvate carboxykinase and NAD-malate dehydrogenase for oxaloacetate produced by the cleavage of citrate in the cytosol.
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PMID:The metabolic fate of the products of citrate cleavage. Adenosine triphosphate-citrate lyase and nicotinamide-adenine dinucleotide phosphate-linked malate dehydrogenase in foetal and adult liver from ruminants and non-ruminants. 438 7

1. Fat-cells isolated from rabbit perirenal adipose tissue were incubated with the following U-(14)C-labelled substrates: 5mm-glucose (+insulin), 5mm-pyruvate, 5mm-lactate, 5mm-glucose+5mm-acetate (+insulin), and the relative rates of incorporation of these substrates into glyceride fatty acids determined. In general total rates of fatty acid synthesis were similar whatever substrate was supplied to the cells. 2. Rabbit fat-cells incorporated [U-(14)C]acetate into fatty acids and CO(2) as well in the absence of glucose as in the presence of this substrate. 3. The disposition of the utilization of glucose-derived carbon through various metabolic pathways was determined. 4. Extramitochondrial and mitochondrial activities were determined for 11 enzymes. The cells contained a very low activity of pyruvate carboxylase, undetectable NADP-malate dehydrogenase activity and a high mitochondrial phosphoenolpyruvate carboxylase activity. 5. Various rabbit fat-cell metabolic parameters based on the measurement of (14)C incorporation and enzyme activity were compared with the same parameters previously measured in rat and guinea-pig fat-cells. In general guinea pig occupied a position between rat and rabbit with respect to these parameters. 6. The profiles of substrate incorporation into fatty acids and of relative enzyme activities in rabbit fat-cells indicated that the operation of a ;citrate-cleavage' pathway may not be obligatory for the supply of lipogenic acetyl units.
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PMID:Lipogenesis in rabbit isolated fat-cells. 447 91

Fatty acid synthesis in adipose tissue normally proceeds at a high rate when fasted animals are refed a diet containing carbohydrate, protein, and low levels of fat. This study investigated the effect of omitting protein from the refeeding diet. Rats were fasted for 48 hr and refed either a protein-free diet or a balanced diet, and the rate of fatty acid synthesis from glucose, pyruvate, lactate, and aspartate was measured. Refeeding the animals a diet devoid of protein resulted in a low rate of fatty acid synthesis from each of these substrates as well as a reduction in carbon flow over the citrate cleavage pathway. The activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, NADP-malate dehydrogenase, and ATP-citrate lyase were also reduced in epididymal fat pads from these rats. On the other hand, adipose tissue phosphoenolpyruvate carboxykinase activity was five times as great as that in tissue from animals refed a balanced diet. This difference could be eliminated if actinomycin D was injected coincident with refeeding. Refeeding rats diets high in carbohydrate is not, therefore, capable of inducing high rates of fatty acid synthesis in adipose tissue in the absence of dietary proteins. Thus, liver and adipose tissue respond differently to dietary protein.
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PMID:Dietary protein and the control of fatty acid synthesis in rat adipose tissue. 534 26

Cells of the aerotolerant anaerobe Giardia lamblia respire in the presence of oxygen. Endogenous respiration is stimulated by glucose but not by other carbohydrates and Krebs cycle intermediates. Endogenous and glucose-stimulated respiration are insensitive to cyanide, malonate, and 2,4-dinitrophenol, but are inhibited by atabrin and iodoacetamide. G. lamblia produces ethanol, acetate and CO2 both aerobically and anaerobically either from endogenous reserves or exogenous glucose. Molecular hydrogen is not produced. The following enzyme activities were detected in homogenates: hexokinase, fructose-biphosphate aldolase, pyruvate kinase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, malate dehydrogenase (decarboxylating), pyruvate synthase, acetyl-CoA synthetase, alcohol dehydrogenase (NADP+), NADH dehydrogenase, NADPH dehydrogenase, NADPH oxidoreductase and superoxide dismutase. The enzymes of energy and carbohydrate metabolism are nonsedimentable (109 000 x g for 30 min). Activities of lactate dehydrogenase, hydrogenase, phosphate acetyltransferase, acetate kinase, citrate synthase, succinate dehydrogenase, fumarate hydratase and catalase were below the limits of detection. The results suggest the occurrence of glycolysis, energy production by substrate level phosphorylation and a flavin, iron-sulfur protein mediated electron transport system as well as the absence of cytochrome mediated oxidative phosphorylation and functional Krebs cycle.
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PMID:Energy metabolism of the anaerobic protozoon Giardia lamblia. 610 7

This work was done to discover how those nonphotosynthetic tissues of the Araceae that become thermogenic release, as CO2, carbon recently fixed by phosphoenolpyruvate carboxylase. Extracts of clubs of the spadix of Arum maculatum showed no activity for phosphoenolpyruvate carboxykinase and low activities of NADP malic enzyme. NAD malic enzyme activity in the above extracts and in those of thermogenic tissues of other Araceae was appreciable. Analysis of homogenates of clubs of Typhonium giraldii by differential centrifugation and sucrose gradients showed that NAD malic enzyme was confined to mitochondria. Centrifugation of mitochondria after freezing and thawing left all the NAD malic enzyme in the supernatant. NAD malic enzyme in isolated, intact mitochondria was completely latent, and was completely protected from exogenous trypsin. The responses of this latency and protection to different concentrations of Triton X-100 suggested that none of the NAD malic enzyme was accessible from either the outside or the intermembrane space of the mitochondria. Treatment of excised clubs of A. maculatum with 2-N-butylmalonate largely prevented the development of the rapid respiration responsible for thermogenesis, and severely inhibited dark fixation of 14CO2. The conclusion is that in mature clubs of the Araceae phosphoenolpyruvate is converted to malate in the cytosol by phosphoenolpyruvate carboxylase and NAD malate dehydrogenase, and that this malate then enters the mitochondrial matrix where it is converted to pyruvate by NAD malic enzyme.
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PMID:Role and location of NAD malic enzyme in thermogenic tissues of Araceae. 642 Dec 32

The object of this work was to investigate the operation of enzymes of the citric acid cycle, the glyoxylate pathway, the glucose metabolism as well as of pyruvate and phosphoenolpyruvate carboxylases in Pseudomonas aeruginosa 640x capable of complete degradation of DDT under the conditions of cometabolism. The activity of isocitrate and glucose-6-phosphate dehydrogenases producing reduced NADP, which is required for reductive dechlorination of DDT, appears to be high. Pyruvate carboxylase and phosphoenolpyruvate carboxylase (EC 4.1.1.31.) function simultaneously in the culture. Differences in the pathways of anaplerotic carbon dioxide fixation were found in P. aeruginosa 640x and the collection strain of P. aeruginosa PAO incapable of DDT degradation.
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PMID:[Central metabolic characteristics of a Pseudomonas aeruginosa culture degrading DDT]. 680 12

It has previously been suggested that the synthesis of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) in Aspergillus nidulans is regulated by a repression-derepression mechanism involving a glycolytic intermediate, and not by induction. Results obtained using compounds that enter the tricarboxylic acid cycle via 2-oxoglutarate, and that can supply both a carbon and a nitrogen source for A. nidulans, suggest it is more likely that the synthesis of phosphoenolpyruvate carboxykinase is inducible, and only weakly regulated by carbon catabolite repression. a similar study of the regulation of the NADP-linked malic enzyme (EC 1.1.1.40) indicates that it too may be inducible.
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PMID:The regulation of phosphoenolpyruvate carboxykinase and the NADP-linked malic enzyme in Aspergillus nidulans. 703 61

With few exceptions, the specific activities of the glycolytic enzymes and the steady-state content of glycolytic and associated intermediates in protoscoleces of the horse (E.g.H) and sheep (E.g.S) strains of Echinococcus granulosus and the closely related E. multilocularis (E.m.) are very similar. Phosphorylase, hexokinase, phosphofructokinase and pyruvate kinase catalyse non-equilibrium reactions and the patterns of activity for pyruvate kinase, phosphoenolypyruvate carboxykinase and malic enzyme are similar in the three organisms. The levels of tricarboxylic acid cycle intermediates in E.g.H., E.g.S. and E.m. are of the same order as those reported in tissues with an active cycle. Each has a complete sequence of cycle enzymes but there are substantial differences between the three parasites with regard to the activity of individual enzymes. The activities of NAD and NADP-linked isocitrate dehydrogenases are significantly lower in E.g.H. than in E.g.S. and particularly in E.m. which suggests that the tricarboxylic acid cycle may play a more important role in carbohydrate metabolism and energy production in the latter parasites. Nevertheless, the three organisms utilize fermentative pathways for alternative energy production, fix carbon dioxide via phosphoenolpyruvate carboxykinase and have a partial reversed tricarboxylic acid cycle. It is speculated that in vivo more carbon will be channelled towards oxaloacetate than pyruvate at the phosphonenolpyruvate branch point. The steady state content of ATP and the ATP/AMP ratios are low in the three organisms, suggesting a low rate of ATP utilization in each.
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PMID:Intermediary carbohydrate metabolism in protoscoleces of Echinococcus granulosus (horse and sheep strains) and E. multilocularis. 707 Aug 45

The activity of enzymes with a regulatory function in the pathways of glycolysis, glyconeogenesis and NADP-generation, and the tissue content of DNA, protein, glycogen, triglycerides (TG), phospholipids (PL), cholesterol and dry matter were investigated in placentas from deliveries accompanied by fetal distress as a result of umbilical cord compression or placental dysfunction in toxemic pregnancies. In placentas from cases of fetal distress due to umbilical cord compression, there was increased activity of pyruvate kinase, 6-phosphogluconate dehydrogenase and NADP-malate dehydrogenase, and decreased activity of phosphoenolpyruvate carboxylase. The activity of aspartate aminotransferase was unchanged, and that of glucose-6-phosphate dehydrogenase was slightly elevated. The tissue content of dry matter, DNA, TG and PL was increased, whereas the protein, cholesterol and glycogen concentrations remained unaltered. In placentas from deliveries accompanied by fetal distress due to placental dysfunction, pyruvate kinase, when calculated per mg protein, was the only enzyme with decreased activity. TG, PL, glycogen and dry matter content were increased, DNA concentration was decreased, and protein and cholesterol remained unchanged. It is suggested that the divergent placental metabolic patterns found in the two fetal distress groups are related to the different levels of disturbed oxygen passage along the uterus-placenta-fetus axis.
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PMID:The placenta in intrauterine fetal deprivation. II. Biochemical profile of placentas from deliveries associated with fetal distress. 735 17


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