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)

The metabolic responses occurring in cucumber (Cucumis sativus L.) roots (a strategy-I plant) grown under iron-deficiency conditions were studied in-vivo using 31P-nuclear magnetic resonance spectroscopy. Iron starvation induced activation of metabolism leading to the consumption of stored carbohydrates to produce the NAD(P)H, ATP and phosphoenolpyruvate necessary to sustain the increased activity of the NAD(P)H:Fe(3+)-reductase, the H(+)-ATPase (EC 3.6.1.35) and phosphoenolpyruvate carboxylase (EC 4.1.1.31). Activation of catabolic pathways was supported by the enhancement of glycolytic enzymes and concentrations of the metabolites glucose-6-phosphate and fructose-6-phosphate, and by enhancement of the respiration rate. Moreover, Fe-deficiency induced a slight increase in the cytoplasmic (pHc) and vacuolar (pHv) pHs as well as a dramatic decrease in the vacuolar phosphate (Pi) concentration. A comparison was done using fusicoccin (FC), a fungal toxin which stimulates proton extrusion. Changes in pHc and pHv were measured after addition of FC. Under these conditions, a dramatic alkalinization of the pHv of -Fe roots was observed, as well as a concomitant Pi movement from the vacuole to the cytoplasm. These results showed that Fe starvation was indeed accompanied by the activation of metabolic processes useful for sustaining the typical responses occurring at the plasma-membrane level (i.e. increases in the NAD(P)H:Fe(3+)-reductase and H(+)-ATPase activities) as well as those involved in the homeostasis of pHc. The decrease in vacuolar Pi levels induced by Fe-deficiency and FC and movement of Pi from the vacuole to the cytoplasm suggest a possible involvement of this compound in the cellular pH-stat system.
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PMID:Metabolic responses in cucumber (Cucumis sativus L.) roots under Fe-deficiency: a 31P-nuclear magnetic resonance in-vivo study. 1087 32

The compartmentation of key processes in sugar, organic acid and amino acid metabolism was studied during the development of the flesh and seeds of grape (Vitis vinifera L.) berries. Antibodies specific for enzymes involved in sugar (cell wall and vacuolar invertases, pyrophosphate: fructose 6-phosphate phosphotransferase, aldolase, NADP-glyceraldehyde-P dehydrogenase, cytosolic fructose 1,6-bisphosphatase), photosynthesis (Rubisco, fructose 1,6-bisphosphatase, sedoheptulose 1,7-bisphosphatase), amino acid metabolism (cytosolic and mitochondrial aspartate aminotransferases, alanine aminotransferase, glutamate dehydrogenase, glutamine synthetase), organic acid metabolism (phosphoenolpyruvate carboxylase, NAD- and NADP-dependent malic enzyme, ascorbate peroxidase), and lipid metabolism (acetyl CoA carboxylase, isocitrate lyase) were used to determine how their abundance changed during development. There were marked changes in the abundance of many of these enzymes in both the flesh and seeds. The intercellular location of some enzymes was investigated using immunohistochemistry. Several enzymes (e.g. phosphoenolpyruvate carboxylase and those involved in amino acid metabolism) were associated with tissues likely to function in the transport of imported assimilates, such as the vasculature. Although other enzymes (e.g. NADP-malic enzyme and soluble acid invertase, involved in the metabolism of sugars and organic acids) were largely present in the parenchyma cells of the flesh, their distribution was extremely heterogeneous. This study shows that when considering the metabolism of complex structures such as fruit, it is essential to consider how metabolism is compartmentalized between and within different tissues, even when they are apparently structurally homogeneous.
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PMID:An immunohistochemical study of the compartmentation of metabolism during the development of grape (Vitis vinifera L.) berries. 1093 59

I compared the C(4) grass flora and climatic records for 32 sites in the United States. Consistent with previous studies, I found that the proportion of the grass flora that uses the NADP malic enzyme (NADP-ME) variant of C(4) photosynthesis greatly increases with increasing annual precipitation, while the proportion using the NAD malic enzyme (NAD-ME) variant (and also the less common phosphoenolpyruvate carboxykinase [PCK] variant) decreases. However the association of grass subfamilies with annual precipitation was even stronger than for the C(4) decarboxylation variants. Analysis of the patterns of distribution by partial correlation analysis showed that the correlations between the frequency of various C(4) types and rainfall were solely due to the association of the C(4) types with particular grass subfamilies. In contrast, there was a strong correlation of the frequency of the different subfamilies with annual precipitation that was independent of the influence of the different C(4) variants. It therefore appears that other, as yet unidentified, characteristics that differ among grass subfamilies may be responsible for their differences in distribution across natural precipitation gradients.
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PMID:Climate and the U.S. distribution of C4 grass subfamilies and decarboxylation variants of C4 photosynthesis. 1094 7

We describe a method for the detection of isoforms of several glycolytic enzymes by activity staining after native PAGE. The staining is based on coupled enzyme assays carried out on the gel after electrophoresis and is linked to the disappearance of NADH, which is visualized by fluorescence. This method offers reliable and sensitive detection for phosphoenolpyruvate carboxylase, PPi-dependent phosphofructokinase, and pyruvate kinase from plant tissues. It can be applied to the detection of all enzymes which are normally detected spectrophotometrically using coupled enzyme assays consuming NAD(P)H.
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PMID:A method for activity staining after native polyacrylamide gel electrophoresis using a coupled enzyme assay and fluorescence detection: application to the analysis of several glycolytic enzymes. 1174 96

The Tn5-induced mutant VG12 of Ralstonia eutropha HF39, which was isolated in this study, revealed an interesting phenotype: it grew on fructose and pyruvate as well as autotrophically like the wild-type, whereas growth on tricarboxylic acid intermediates and glyoxylic acid was reduced, and no growth occurred if acetate, propionate or levulinate were provided as carbon source. Tn5 was mapped in a gene encoding an NAD(H)-dependent malate dehydrogenase (MDH), and MDH activity was strongly diminished in VG12. Furthermore, the mdh gene was cloned, sequenced and heterologously expressed in Escherichia coli, conferring significantly higher specific MDH activity to the recombinant strain. The phenotype of VG12 sheds light on the C(3)/C(4) metabolism of R. eutropha, which mediates between the Entner-Doudoroff pathway and the tricarboxylic acid cycle (TCC), demonstrating that enzymes catalyzing the conversion of C(3) and C(4) metabolites can circumvent the metabolic disruption of the TCC in VG12 and that the phosphoenolpyruvate carboxykinase serves a dual and important function.
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PMID:The malate dehydrogenase of Ralstonia eutropha and functionality of the C(3)/C(4) metabolism in a Tn5-induced mdh mutant. 1211 28

The effects of benfluorex and two of its metabolites (S 422-1 and S 1475-1) on fatty acid and glucose metabolic fluxes and specific gene expression were studied in hepatocytes isolated from 24-h fasted rats. Both benfluorex and S 422-1 (0.1 or 1 mmol/l) reduced beta-oxidation rates and ketogenesis, whereas S 1475-1 had no effect. At the same concentration, benfluorex and S 422-1 were more efficient in reducing gluconeogenesis from lactate/pyruvate than S 1475-1. Benfluorex inhibited gluconeogenesis at the level of pyruvate carboxylase (45% fall in acetyl-CoA concentration) and of glyceraldehyde-3-phosphate dehydrogenase (decrease in ATP/ADP and NAD(+)/NADH ratios). Accordingly, neither benfluorex nor S 422-1 inhibited gluconeogenesis from dihydroxyacetone, but both stimulated gluconeogenesis from glycerol. In hepatocytes cultured in the presence of benfluorex or S 422-1 (10 or 100 micromol/l), the expression of genes encoding enzymes of fatty acid oxidation (carnitine palmitoyltransferase [CPT] I), ketogenesis (hydroxymethylglutaryl-CoA synthase), and gluconeogenesis (glucose-6-phosphatase, PEPCK) was decreased, whereas mRNAs encoding glucokinase and pyruvate kinase were increased. By contrast, Glut-2, acyl-CoA synthetase, and CPT II gene expression was not affected by benfluorex or S 422-1. In conclusion, this work suggests that benfluorex mainly via S 422-1 reduces gluconeogenesis by affecting gene expression and metabolic status of hepatocytes.
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PMID:Effects of benfluorex on fatty acid and glucose metabolism in isolated rat hepatocytes: from metabolic fluxes to gene expression. 1214 46

Strategy I plants respond to Fe deficiency by inducing morphological and biochemical modifications at the root level that are apt to make iron available for uptake. Cucumber (Cucumis sativus L.) grown in the absence of Fe has been shown to increase the capacity to acidify the rhizosphere and Fe3+ reduction activity. We have determined in these roots some metabolic activities that might be correlated with the increased proton extrusion. Proton efflux from roots may be followed by a mechanism regulating the cytosolic pH according to the pH-stat theory. Roots grown in the absence of Fe showed an increase in dark 14CO2 fixation and organic acid synthesis and a 6-fold increase in the extractable phosphoenolpyruvate carboxylase activity with respect to the control roots. Dehydrogenase activities producing cytosolic NAD(P)H were also increased under Fe deficiency. The presence of Fe2+, but not Fe3+, inhibited dark 14CO2 fixation in a range between 24 and 52% but did not show any effect on the in vitro phosphoenolpyruvate carboxylase activity.
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PMID:Metabolic Implications in the Biochemical Responses to Iron Deficiency in Cucumber (Cucumis sativus L.) Roots. 1222 26

Embryo axes isolated from germinating lupine seeds were cultivated in vitro for 24-96 h over media containing either 60 mmol/L sucrose or no sucrose. Ultrastructural studies showed that large vacuoles were accumulating in a central region of primary parenchyma cells in sucrose starved lupine embryo axes, whereas cytoplasm along with organelles were forced to a periphery of the cells. We suggest that the autolysis of cytoplasmic proteins contributes to the accumulation of the vacuoles and this suggestion is consistent with the results of the characterisation of protein content. The level of cytosolic proteins was reduced by 50% and the activity of cytosolic marker enzyme, PEP carboxylase, was reduced by 46% in starved embryos as compared to control. The mitochondria from starved tissues were not degraded. The level of mitochondrial proteins was reduced by only 10% and the activity of mitochondrial NAD-isocitrate dehydrogenase decreased by 8% as a result of starvation. As demonstrated by the results of Percoll density gradient centrifugation, sucrose starvation caused an increase of 49% in many of the higher density mitochondria fractions, whereas many of the lower density mitochondria fractions were decreased by 33%. The samples of mitochondria from starved embryo axes were determined to have higher respiration activity in the presence of glutamate and malate as compared to control samples. EPR-based analyses of free radicals showed the presence of free radicals with a signal at g = 2.0060 in embryo axes. The level of the radical was two times higher in sucrose-starved embryo axes than in control (the level of this radical increased in senescing plant tissues as well). The results of EPR-based quantitation of Mn2+ ions revealed that the level was a few times higher in starved material than in control. Starved embryo axes, however, do possess a number of adaptive mechanisms protecting them from oxidative damage. Densitometric analyses of gels revealed an increase in the activity of SOD in sugar-starved embryos, whereas CAT and POX activities were lower in axes grown without sucrose as compared to control. Superoxide dismutase, catalase and peroxidase zymogram analyses showed that synthesis of new isoforms was not induced by sugar starvation. An accumulation of phytoferritin was found in plastids of sucrose starved embryos. These results are discussed in relation to the metabolic changes observed in senescing plant tissues.
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PMID:Metabolic and ultrastructural responses of lupine embryo axes to sugar starvation. 1274 88

A comprehensive network structure for the autotrophic growth of Arthrospira platensis is proposed. The metabolic network was built up with 121 reactions and 134 metabolites including biomass synthesis, production of a growth-associated exopolysaccharide, and energy aspects. The model supports the existence of a metabolic shunt of PEP to pyruvate through PEP carboxylase, NAD(+)-dependent malate dehydrogenase and malic enzyme to convert NADH,H(+) into NADPH,H(+). A limit in Arthrospira growth metabolism due to NADH,H(+) balancing is evidenced, explaining why the maximal light-dependent mass yield of the growth-associated exopolysaccharide was 0.51 kg EPS kg(-1) biomass, consistent with experimental results.
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PMID:Identification of a metabolic network structure representative of Arthrospira (spirulina) platensis metabolism. 1459 79

To express foreign proteins in Actinobacillus succinogenes, a shuttle vector was constructed based on the Actinobacillus pleuropneumoniae-Escherichia coli shuttle vector, pGZRS-19. We demonstrated that A. succinogenes is transformed by electroporation at reasonably high efficiency, that pGZRS-19 is stable in A. succinogenes, and that the ampicillin resistance gene carried by pGZRS-19 is expressed in A. succinogenes. Three steps were then required to develop our A. succinogenes-E. coli shuttle vector. (i) The constitutively expressed A. succinogenes phosphoenolpyruvate carboxykinase gene, pckA, was cloned and sequenced. (ii) Its promoter region and ribosome-binding site were subcloned into pGZRS-19. (iii) Finally, the ColE1 origin of replication was added to the vector to increase its stability in E. coli. High levels of A. succinogenes phosphoenolpyruvate carboxykinase, E. coli NADP-dependent malic enzyme, and Bacillus subtilis NAD-dependent malic enzyme activities detected in recombinant A. succinogenes strains confirmed that A. succinogenes and foreign proteins could be expressed in A. succinogenes under control of the A. succinogenes pckA promoter carried by pLGZ920. A. succinogenes is sensitive to chloramphenicol and tetracycline. Although not expressed from their own promoters, the Tn9 chloramphenicol and the Tn10 tetracycline resistance genes are expressed under control of the pckA promoter, and they can be used as additional selection markers in A. succinogenes.
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PMID:Construction of a shuttle vector for the overexpression of recombinant proteins in Actinobacillus succinogenes. 1500 7


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