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)

Comparison of the activities of hexokinase, phosphorylase and phosphofructokinase in muscles from marine invertebrates indicates that they can be divided into three groups. First, the activities of the three enzymes are low in coelenterate muscles, catch muscles of molluscs and muscles of echinoderms; this indicates a low rate of carbohydrate (and energy) utilization by these muscles. Secondly, high activities of phosphorylase and phosphofructokinase relative to those of hexokinase are found in, for example, lobster abdominal and scallop snap muscles; this indicates that these muscles depend largely on anaerobic degradation of glycogen for energy production. Thirdly, high activities of hexokinase are found in the radular muscles of prosobranch molluscs and the fin muscles of squids; this indicates a high capacity for glucose utilization, which is consistent with the high activities of enzymes of the tricarboxylic acid cycle in these muscles [Alp, Newsholme & Zammit (1976) Biochem. J. 154, 689-700]. 2. The activities of lactate dehydrogenase, octopine dehydrogenase, phosphoenolpyruvate carboxykinase, cytosolic and mitochondrial glycerol 3-phosphate dehydrogenase and glutamate-oxaloacetate transaminase were measured in order to provide a qualitative indication of the importance of different processes for oxidation of glycolytically formed NADH. The muscles are divided into four groups: those that have a high activity of lactate dehydrogenase relative to the activities of phosphofructokinase (e.g. crustacean muscles); those that have high activities of octopine dehydrogenase but low activities of lactate dehydrogenase (e.g. scallop snap muscle); those that have moderate activities of both lactate dehydrogenase and octopine dehydrogenase (radular muscles of prosobranchs), and those that have low activities of both lactate dehydrogenase and octopine dehydrogenase, but which possess activities of phosphoenolpyruvate carboxykinase (oyster adductor muscles). It is suggested that, under anaerobic conditions, muscles of marine invertebrates form lactate and/or octopine or succinate (or similar end product) according to the activities of the enzymes present in the muscles (see above). The muscles investigated possess low activities of cytosolic glycerol 3-phosphate dehydrogenase, which indicates that glycerol phosphate formation is quantitatively unimportant under anaerobic conditions, and low activities of mitochondrial glycerol phosphate dehydrogenase, which indicates that the glycerol phosphate cycle is unimportant in the re-oxidation of glycolytically produced NADH in these muscles under aerobic conditions. Conversely, high activities of glutamate-oxaloacetate transaminase are present in some muscles, which indicates that the malate-aspartate cycle may be important in oxidation of glycolytically produced NADH under aerobic conditions. 3. High activities of nucleoside diphosphate kinase were found in muscles that function for prolonged periods under anaerobic conditions (e.g...
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PMID:The maximum activities of hexokinase, phosphorylase, phosphofructokinase, glycerol phosphate dehydrogenases, lactate dehydrogenase, octopine dehydrogenase, phosphoenolpyruvate carboxykinase, nucleoside diphosphatekinase, glutamate-oxaloacetate transaminase and arginine kinase in relation to carbohydrate utilization in muscles from marine invertebrates. 1 83

Phytomonas sp. isolated from Euphorbia characias was adapted to SDM-79 medium. Cells isolated in the early stationary phase of growth were analyzed for their capacity to utilize plant carbohydrates for their energy requirements. The cellulose-degrading enzymes amylase, amylomaltase, invertase, carboxymethylcellulase, and the pectin-degrading enzymes polygalacturonase and oligo-D-galactosiduronate lyase were present in Phytomonas sp. and were all, except for amylomaltase, excreted into the external medium. Glucose, fructose and mannose served as the major energy substrates. Catabolism of carbohydrates occurred mainly via aerobic glycolysis according to the Embden-Meyerhof pathway, of which all the enzymes were detected. Likewise, the end-products of glycolysis, acetate and pyruvate, glycerol, succinate and ethanol were detected in the culture medium, as were the enzymes responsible for their production. Mitochondria were incapable of oxidizing succinate, 2-oxoglutarate, pyruvate, malate and proline, but had a high capacity to oxidize glycerol 3-phosphate. This oxidation was completely inhibited by salicylhydroxamic acid. No cytochromes could be detected either in intact mitochondria or in sub-mitochondrial particles. Mitochondrial respiration was not inhibited by antimycin, azide or cyanide. The glycolytic enzymes, from hexokinase to phosphoglycerate kinase, and the enzymes glycerol kinase, glycerol-3-phosphate dehydrogenase, phosphoenolpyruvate carboxykinase, malate dehydrogenase and adenylate kinase, were all associated with glycosomes that had a buoyant density of about 1.24 g cm-1 in sucrose. Cytochemical staining revealed the presence of catalase in these organelles. The cytosolic enzyme pyruvate kinase was activated by fructose 2,6-bisphosphate, typical of all other pyruvate kinases from Kinetoplastida. The energy metabolism of the plant parasite Phytomonas sp. isolated from E. characias resembled that of the bloodstream form of the mammalian parasite Trypanosoma brucei.
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PMID:Characterization of carbohydrate metabolism and demonstration of glycosomes in a Phytomonas sp. isolated from Euphorbia characias. 143 59

The expression of glutamine synthetase (GS) in the rat liver is dependent on pituitary growth hormone (GH). RNA blot hybridizations revealed that in hypophysectomized rats the level of glutamine synthetase mRNA was dramatically reduced in liver but not brain. This drop of GS mRNA in the liver results in a reduction of GS enzyme activity as well. Two other messages, phosphoenolpyruvate carboxykinase and glycerol phosphate dehydrogenase were not diminished in the liver, indicating that the effects of hypophysectomy on hepatic GS expression are specific and not part of a general reduction in transcription due to lack of pituitary factors. Daily administration of rat pituitary growth hormone caused an increase in the levels of hepatic GS mRNA as well as enzyme activity. In situ hybridization of normal liver sections with the GS antisense message showed an abundant amount of message confined to the region around each central vein of the hepatic acini, while in the hypophysectomized animal the message for GS is greatly reduced but still only located in hepatocytes surrounding the central vein. Hypophysectomized animals given GH replacement showed a substantial increase in the amount of exposed silver grains only around the central veins. This indicates that GH does not influence the cellular position of GS expression nor the viability of those hepatocytes that express the enzyme, but it does regulate the quantity of GS in the liver through changes in the levels of GS mRNA.
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PMID:Growth hormone regulation of hepatic glutamine synthetase mRNA levels in rats. 197 Mar 14

The adipose conversion of Ob1771 and 3T3-F442A preadipose cells is accompanied by the expression of the phosphoenolpyruvate carboxykinase (PEPCK) gene. The PEPCK mRNA is absent from growing, undifferentiated Ob1771 and 3T3-F442A cells as well as from non-differentiating 3T3-C2 cells. It is present in differentiated Ob1771 and 3T3-F442A cells as well as in liver, kidney and white adipose tissue from mouse. Transcriptional run-off measurements in nuclei isolated from undifferentiated and differentiated Ob1771 and 3T3-F442A cells reveal that the PEPCK gene transcription is activated during differentiation. Studies of the time course of changes indicate that the emergence of PEPCK mRNA takes place in parallel to mRNA encoding for a 28 kDa protein (28 K mRNA) but later than that encoding for glycerol-3-phosphate dehydrogenase (GPDH mRNA). Insulin leads to an increase in the content of PEPCK and GPDH mRNAs with half-maximally effective concentrations of 0.5 and 5 nM for GPDH mRNA and PEPCK mRNA, respectively. Thus, in contrast to rat hepatoma cells, insulin exerts in adipose cells a positive regulation on the expression of the PEPCK gene.
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PMID:Expression of the phosphoenolpyruvate carboxykinase gene and its insulin regulation during differentiation of preadipose cell lines. 352 64

The present study was undertaken to measure the activities of several hepatic enzymes of regulatory importance in the pathways of lipogenesis and gluconeogenesis in rats fed diets marginally deficient in copper (1.2 micrograms Cu/g of diet) and containing either fructose, glucose, or starch as the carbohydrate sources. Although all copper-deficient rats exhibited the characteristic signs of copper deficiency, they were more pronounced in rats fed the diet containing fructose. Except for the activity of phosphoenolpyruvate carboxykinase which was unaffected either by copper deficiency or by the type of dietary carbohydrate, the hepatic activities of glucose-6-phosphate dehydrogenase, malic enzyme, L-alpha-glycerophosphate dehydrogenase and fructose 1,6-diphosphatase were unaffected by copper deficiency but were affected by the type of carbohydrate in the diet. Fructose produced the greatest increase in enzymatic activities, whereas starch produced the least activity and glucose induced an intermediate effect. These results indicate that the deleterious effects of a fructose diet deficient in copper on biochemical and physiological indices could not be due to an immediate metabolite of fructose. However, the involvement of a subsequent metabolite of fructose in the mechanism of copper utilization and/or requirement cannot be excluded.
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PMID:Effects of different dietary carbohydrates on hepatic enzymes of copper-deficient rats. 397 25

Glutathione-depleted hepatocytes, by incubation with diethylmaleate (DEM) or phorone (2,6-dimethyl-2,5-heptadiene-4-one), i.e., substrates of the GSH S-transferases (EC 2.5.1.18), showed rates of gluconeogenesis from various precursors significantly lower than controls; however the rate of glucose synthesis from fructose was similar to that of controls. Isolated hepatocytes from rats pretreated with those substrates 1 h before isolation to deplete hepatic glutathione (GSH) also showed a decrease of the rate of gluconeogenesis from lactate plus pyruvate. Incubation of hepatocytes with L-buthionine sulfoximine, a specific inhibitor of gamma-glutamyl-cysteine synthetase (EC 6.3.2.2), resulted in a decreased rate of gluconeogenesis from lactate plus pyruvate only when GSH values were lower than 1 mumol/g cells. Freeze-clamped livers from GSH-depleted rats showed a higher concentration of malate and glycerol 3-phosphate, indicating that GSH depletion probably affects phosphoenolpyruvate carboxykinase and glycerol-3-phosphate dehydrogenase activities. Several indicators of cell viability, such as lactate dehydrogenase leakage, malondialdehyde accumulation, ATP concentration, or urea synthesis from different precursors, were not affected by GSH depletion under the experimental conditions used here. Besides, the GSH/GSSG ratio remained unchanged in all cases.
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PMID:Effects of glutathione depletion on gluconeogenesis in isolated hepatocytes. 402 24

Triiodothyronine (T3) treatment of pregnant rats for 6 days, 10 micrograms/100 g, resulted in a pronounced induction of enzymes related to gluconeogenesis and lipogenesis and of mitochondrial FAD-glycerophosphate dehydrogenase in the maternal liver, as previously observed in male rats. There was virtually no change in the activity of these enzymes in the placenta. However, there was a distinct induction of these enzymes in the fetal liver, even if increments in fetal serum and liver T3 were much smaller than on the maternal side. This indicates that changes in hepatic enzyme activities are a more sensitive index of fetal hyperthyroidism than T3 levels. The increased lipogenic capacity was expressed by greater incorporation of a tritium tracer into fatty acids. Administration of triamcinolone, 2 mg/100 g, for the last 5 days of gestation resulted in marked induction of maternal hepatic enzymes of lipogenesis, gluconeogenesis and of aspartate aminotransferase (ASAT), known to occur in male rats, as well as in a metabolic pattern of insulin resistance. The response of placental enzymes was limited to a small elevation in ASAT and phosphoenolpyruvate carboxykinase (PEPCK) activity. In the fetal liver there was no stimulation of lipogenic enzymes, but a marked induction of PEPCK and ASAT. The changes in the lipogenic capacity were confirmed by tritium incorporation into serum and liver fatty acids. These results demonstrate the marked sensitivity of specific fetal enzyme systems to the maternal iatrogenic hyperthyroidism or hypercorticism. The limited alterations in placental enzyme activities are in accord with the concept that placental metabolic stability fulfils a protective function toward the fetus.
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PMID:Modulation of fetal and placental metabolic pathways in response to maternal thyroid and glucocorticoid hormone excess. 813 95

Cytosolic phosphoenolpyruvate carboxykinase (PEPCK) plays a critical role in adipose tissue glyceroneogenesis. We have previously shown that transcription of the PEPCK gene was stimulated by isoprenaline and retinoic acid in 3T3-F442A adipocytes. We also showed that oleate increased PEPCK mRNA. Here, we analysed the effect that fatty acids of various chain lengths and unsaturation degrees exerted on PEPCK gene expression in 3T3-F442A adipocytes. When maintained in serum-free, glucose-free medium, differentiated cells responded to unsaturated long-chain fatty acids by a large increase in PEPCK mRNA whereas saturated fatty acids were inefficient. A maximum fivefold stimulation by oleate was attained at 4 h of treatment with 1 mM fatty acid bound to albumin in a 6:1 ratio. The poly-unsaturated very long-chain fatty acid all-cis-4,7,10,13,16,19-docosahexaenoic acid (C22:6) was even more potent and produced a tenfold increase. The expression of the genes encoding glycerol-3-phosphate dehydrogenase, hormone-sensitive lipase or actin remained unaffected by oleate exposure. A 4-h treatment by the hypolipidemic drug clofibrate, 0.5-2 mM, also produced a large (3-9-fold) increase in PEPCK mRNA. When used at non-saturating concentrations, oleate and clofibrate acted in an additive manner. At maximally effective concentrations, additivity was lost, suggesting that fatty acids and fibrates might act through similar mechanisms. Nuclear transcription experiments showed that oleate and clofibrate stimulated the transcription rate of the gene. 3T3-F442A cells were stably transfected with a plasmid containing the base pairs -2100 to +69 of the PEPCK gene promoter fused to the chloramphenicol acetyltransferase gene. These differentiated stable transfectants responded to oleate and clofibrate by a specific increase in chloramphenicol acetyltransferase activity. Adipocytes express various isoforms of peroxisome-proliferator-activated receptors that can be activated by fibrates and fatty acids. Potential recognition sequences for peroxisome-proliferator-activated receptors are present in the -2100 to +69 fragment of the PEPCK gene promoter. Thus, this gene represents an ideal molecular target for understanding the complex transcriptional control exerted by fatty acids and peroxisome proliferators.
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PMID:Fatty acids and fibrates are potent inducers of transcription of the phosphenolpyruvate carboxykinase gene in adipocytes. 853 80

Theileria parva schizonts propagated in vitro in peripheral blood lymphocytes were purified and assayed for key enzymes of glucose and glycerol catabolism and the citric acid cycle. The activities of glycolytic enzymes were in the range of 21-100 nmol/min/mg protein. Glycerol kinase and alpha -glycerophosphate dehydrogenase activities were more than 16 times lower than the activities of other enzymes catalysing the oxidation of the triose phosphates to lactate. It was suggested that the catabolism of glycerol is negligible and that glucose is catabolized to lactate via the Embden-Meyerhof pathway. The activities of the enzymes catalysing the section of the citric acid cycle that involves the formation of citrate to succinyl-CoA were consistently very low (less than 2.0 nmol/min/mg protein), indicating that this part of the cycle plays a minor role in this parasite. Enzyme activities of the cycle catalysing the formation of succinate from oxaloacetate were relatively higher than those catalysing other sections of the citric acid cycle, suggesting that this section of the cycle could be important to the parasite. Pyruvate carboxylase activity was more than 10 times that of phosphoenolpyruvate carboxykinase. It was suggested that pyruvate could be carboxylated to oxaloacetate. Taken together, these results suggest that the catabolism of glucose in Theileria parva schizonts is mainly via the Embden-Meyerhof pathway and that the citric acid cycle plays a minor role in energy production.
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PMID:Enzymes of glucose and glycerol catabolism in in vitro-propagated Theileria parva schizonts. 1055 43

Activities of enzymes associated with glycerol synthesis were compared in the liver of two osmerid fishes, the smelt (Osmerus mordax), which can accumulate high (400 mM) levels of glycerol and capelin (Mallotus villosus) that does not accumulate glycerol. Animals were sampled at approximately the same time of year and temperature thus negating potential seasonal effects. These species are closely related, reducing interpretative issues involving comparison between unrelated species. We found that key enzyme activities were elevated in the smelt relative to the non-glycerol accumulating capelin, namely enzymes involved with glycolysis (phosphofructose kinase-1 and aldolase), amino acid metabolism (aspartate aminotransferase and alanine aminotransferase), gluconeogenesis (phosphoenolpyruvate carboxykinase) and glycerol synthesis (glycerol-3-phosphate dehydrogenase). The enzyme profiles strongly support the hypothesis that smelt can synthesize glycerol by utilizing glycogen and amino acids as the carbon source and that they have increased capacity for metabolic flux through loci required for synthesis of the three carbon intermediate dihydroxyacetone phosphate and subsequently glycerol synthesis.
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PMID:Comparison of liver enzymes in osmerid fishes: key differences between a glycerol accumulating species, rainbow smelt (Osmerus mordax), and a species that does not accumulate glycerol, capelin (Mallotus villosus). 1202 Jun 59


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