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)

Lactate and succinate were produced from glucose by Corynebacterium glutamicum under oxygen deprivation conditions without growth. Addition of bicarbonate to the reaction mixture led not only to a 3.6-fold increase in succinate production rate, but also to a 2.3- and 2.5-fold increase, respectively, of the rates of lactate production and glucose consumption, compared to the control. Furthermore, when small amounts of pyruvate were added to the reaction mixture, acid production rates and the glucose consumption rate were multiplied by a factor ranging from 2 to 3. These phenomena were paralleled by an increase in the NAD(+)/NADH ratio, thus corroborating the view that the efficient regeneration of NAD(+) could be triggered by the addition of either bicarbonate or pyruvate. To investigate the global metabolism of corynebacteria under oxygen deprivation conditions, we engineered several strains where the genes coding for key metabolic enzymes had been inactivated by gene disruption and replacement. A lactate dehydrogenase (LDH)-deficient mutant was not able to produce lactate, suggesting this enzyme has no other isozyme. Although a pyruvate carboxylase (pyc) mutant exhibited similar behavior to that of the wild type, phosphoenolpyruvate carboxylase (ppc) mutants were characterized by a dramatic decrease in succinate production, which was concomitant to decreased lactate production and glucose consumption rates. This set of observations corroborates the view that in coryneform bacteria under oxygen deprivation conditions the major anaplerotic reaction is driven by the ppc gene product rather than by the pyc gene product. Moreover, intracellular NADH concentrations in C. glutamicum were observed to correlate to oxygen-deprived metabolic flows.
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PMID:Metabolic analysis of Corynebacterium glutamicum during lactate and succinate productions under oxygen deprivation conditions. 1538 16

Sorghum vulgare phosphoenolpyruvate carboxylase (PEPC) and Lactococcus lactis pyruvate carboxylase (PYC) were overexpressed in Escherichia coli concurrently to improve the production of succinate, a valuable industrial specialty chemical. This coexpression system was also applied to E. coli mutant strains strategically designed by inactivating the competing pathways of succinate formation. The highest level of succinate production was observed in E. coli strains coexpressing both PEPC and PYC when compared with E. coli strains individually overexpressing either PEPC or PYC. Lactate production was also significantly reduced with PEPC and PYC coexpression. Lactate and acetate pathways were inactivated to eliminate the competing pathways of succinate formation. Results showed that inactivation of both the lactate and acetate pathways with the coexpression of PEPC and PYC was most effective in improving succinate production. Inactivating the lactate or acetate pathway alone only caused a majority of the carbon flux to shift to other metabolites rather than succinate. Coexpression of PEPC and PYC was also applied to an E. coli mutant strain deficient in lactate dehydrogenase and pyruvate:formate lyase that accumulated a substantial amount of the intermediate metabolite pyruvate during growth. Results showed that PEPC and PYC coexpression was effective in depleting pyruvate accumulation and increasing the production of metabolites.
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PMID:Effect of Sorghum vulgare phosphoenolpyruvate carboxylase and Lactococcus lactis pyruvate carboxylase coexpression on succinate production in mutant strains of Escherichia coli. 1556 33

The effects of several single-gene knockout mutants (pykF, ppc, pflA, pta, and adhE mutants) on the metabolic flux distribution in Escherichia coli were investigated under microaerobic condition. The intracellular metabolite concentrations and enzyme activities were measured, and the metabolic flux distribution was computed to study the metabolic regulation in the cell. The pflA, pta and ppc mutants produced large amount of lactate when using glucose as a carbon source under microaerobic condition. Comparing the flux distribution and the enzyme activities in the mutants, it was shown that the lactate production was promoted by the inactivation of pyruvate formate lyase and the resulting overexpression of lactate dehydrogenase. The flux through Pta-Ack pathways and the ethanol production were limited by the available acetyl coenzyme A. It was shown that the glycolysis was activated in pykF mutant in microaerobic culture. The glycolytic flux was related with Pyk activity except for pykF mutant. The cell growth rate was shown to be affected by the flux through phosphoenolpyruvate carboxylase. The quantitative regulation analysis was made based on the deviation indexes.
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PMID:Effect of a single-gene knockout on the metabolic regulation in Escherichia coli for D-lactate production under microaerobic condition. 1578 19

The central metabolic pathway of Corynebacterium glutamicum was engineered to produce ethanol. A recombinant strain which expressed the Zymomonas mobilis genes coding for pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adhB) was constructed. Both genes placed under the control of the C. glutamicum ldhA promoter were expressed at high levels in C. glutamicum, resulting, under oxygen-deprivation conditions, in a significant yield ofethanol from glucose in a process characterized by the absence of cellular growth. Addition of pyruvate in trace amounts to the reaction mixture induced a 2-fold increase in the ethanol production rate. A similar effect was observed when acetaldehyde was added. Disruption of the lactate dehydrogenase (ldhA) gene led to a 3-fold higher ethanol yield than wild type, with no lactate production. Moreover, inactivation of the phosphoenolpyruvate carboxylase (ppc) and ldhA genes revealed a significant amount of ethanol production and a dramatic decrease in succinate without any lactate production, when pyruvate was added. Since the reaction occurred in the absence of cell growth, the ethanol volumetric productivity increased in proportion to cell density of ethanologenic C. glutamicum in a process under oxygen-deprivation conditions. These observations corroborate the view that intracellular NADH concentrations in C. glutamicum are correlated to oxygen-deprived metabolic flows.
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PMID:Metabolic engineering of Corynebacterium glutamicum for fuel ethanol production under oxygen-deprivation conditions. 1617 1

Growth and succinate versus lactate production from glucose by Anaerobiospirillum succiniciproducens was regulated by the level of available carbon dioxide and culture pH. At pH 7.2, the generation time was almost doubled and extensive amounts of lactate were formed in comparison with growth at pH 6.2. The succinate yield and the yield of ATP per mole of glucose were significantly enhanced under excess-CO(2)-HCO(3) growth conditions and suggest that there exists a threshold level of CO(2) for enhanced succinate production in A. succiniciproducens. Glucose was metabolized via the Embden-Meyerhof-Parnas route, and phosphoenolpyruvate carboxykinase levels increased while lactate dehydrogenase and alcohol dehydrogenase levels decreased under excess-CO(2)-HCO(3) growth conditions. Kinetic analysis of succinate and lactate formation in continuous culture indicated that the growth rate-linked production rate coefficient (K) cells was much higher for succinate (7.2 versus 1.0 g/g of cells per h) while the non-growth-rate-related formation rate coefficient (K') was higher for lactate (1.1 versus 0.3 g/g of cells per h). The data indicate that A. succiniciproducens, unlike other succinate-producing anaerobes which also form propionate, can grow rapidly and form high final yields of succinate at pH 6.2 and with excess CO(2)-HCO(3) as a consequence of regulating electron sink metabolism.
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PMID:Influence of CO(2)-HCO(3) Levels and pH on Growth, Succinate Production, and Enzyme Activities of Anaerobiospirillum succiniciproducens. 1634 70

Anadromous arctic char (Salvelinus alpinus) undertake short feeding migrations to seawater every summer and accumulate lipids, while the rest of the year is spent in fresh water where the accumulated lipid reserves are mobilized. We tested the hypothesis that winter fasting and the associated polychlorinated biphenyls' (PCBs) redistribution from lipid depots to critical tissues impair the liver metabolic capacity in these animals. Char were administered Aroclor 1254 (0, 1, 10, and 100 mg/kg body mass) orally and maintained for 4 months without feeding to mimic seasonal winter fasting, while fed groups (0 and 100 mg Aroclor 1254/kg) were maintained for comparison. A clear dose-related increase in PCB accumulation and cytochrome P4501A (CYP1A) protein content was observed in the livers of fasted fish. This PCB concentration and CYP1A response with the high dose of Aroclor were 1.5-fold and 3-fold greater in the fasted than in the fed fish, respectively. In fed fish, PCB exposure lowered liver glycogen content, whereas none of the other metabolic indicators were significantly affected. In fasted fish, PCB exposure depressed liver glycogen content and activities of glucose-6-phosphate dehydrogenase, alanine aminotransferase, lactate dehydrogenase, and phosphoenolpyruvate carboxykinase and elevated 3-hydroxyacylcoA dehydrogenase activity and glucocorticoid receptor protein expression. There were no significant impacts of PCB on heat shock protein 70 (hsp70) and hsp90 contents in either fed or fasted fish. Collectively, our study demonstrates that winter emaciation associated with the anadromous lifestyle predisposes arctic char to PCB impact on hepatic metabolism including disruption of the adaptive metabolic responses to extended fasting.
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PMID:Fasting augments PCB impact on liver metabolism in anadromous arctic char. 1653 58

The rate of phosphoenolpyruvate carboxylase activity measured through the conventional coupled assay with malate dehydrogenase is underestimated due to the instability of oxaloacetate, which undergoes partial decarboxylation into pyruvate in the presence of metal ions. The addition of lactate dehydrogenase to the conventional assay allows the reduction of pyruvate formed from oxaloacetate to lactate with the simultaneous oxidation of NADH. Then, the enzymic determination of substrate and products shows that the combined activities of malate dehydrogenase and lactate dehydrogenase account for all the phosphoenolpyruvate consumed. The net result of the improved assay is a higher V(max) with no apparent effect on K(m). The free divalent cation concentration appears to be the major factor in the control of the rate of oxaloacetate decarboxylation.
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PMID:A simple and accurate spectrophotometric assay for phosphoenolpyruvate carboxylase activity. 1666 4

The aim of this work was to discover the extent of interference by phosphoenolpyruvate (PEP) phosphatase in spectrophotometric assays of PEP carboxylase (EC 4.1.1.31) in crude extracts of plant organs. The presence of PEP phosphatase and lactate dehydrogenase (EC 1.1.1.27) in extracts leads to PEP-dependent NADH oxidation that is independent of PEP carboxylase activity, and hence to overestimation of PEP carboxylase activity. In extracts of three organs of pea (Pisum sativum L.: leaves, developing embryos, and Rhizobium nodules), two organs of wheat (Triticum aestivum L.: developing grain and endosperm), and leaves of Moricandia arvensis (L.) D.C., lactate dehydrogenase activity was at most only 16% of that of PEP carboxylase at the pH optimum for PEP carboxylase activity. Endogenous PEP phosphatase and lactate dehydrogenase are thus unlikely to interfere seriously with the assay for PEP carboxylase at its optimum pH. Addition of lactate dehydrogenase to PEP carboxylase assays- a proposed means of correcting for nonenzymic decarboxylation of oxaloacetate to pyruvate-resulted in increases in PEP-dependent NADH oxidation from zero (Rhizobium nodules) to 131% (wheat grains). There was no obvious relationship between the magnitude of this increase and conditions in the assay that might promote oxaloacetate decarboxylation. However, the magnitude of the increase was highly positively correlated with the activity of PEP phosphatase in the extract. Addition of lactate dehydrogenase to PEP carboxylase assays can thus result in very large overestimations of PEP carboxylase activity, and should only be used as a means of correction for oxaloacetate decarboxylation for extracts with negligible PEP phosphatase activity.
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PMID:Interference by phosphatases in the spectrophotometric assay for phosphoenolpyruvate carboxylase. 1666 52

Metabolically engineered Escherichia coli has previously been used to degrade cis-1,2-dichloroethylene (cis-DCE). The strains express the six genes of an evolved toluene ortho-monooxygenase from Burkholderia cepacia G4 (TOM-Green, which formed a reactive epoxide) with either (1) gamma-glutamylcysteine synthetase (GSHI, which forms glutathione) and the glutathione S-transferase IsoILR1 from Rhodococcus AD45 (which adds glutathione to the reactive cis-DCE epoxide) or (2) with an evolved epoxide hydrolase from Agrobacterium radiobacter AD1 (EchA F108L/I219L/C248I which converts the reactive cis-DCE epoxide to a diol). Here, the impact of this metabolic engineering for bioremediation was assessed by investigating the changes in the proteome through a quantitative shotgun proteomics technique (iTRAQ) by tracking the changes due to the sequential addition of TOM-Green, IsoILR1, and GSHI and due to adding the evolved EchA versus the wild-type enzyme to TOM-Green. For the TOM-Green/EchA system, 8 proteins out of 268 identified proteins were differentially expressed in the strain expressing EchA F108L/I219L/C248I relative to wild-type EchA (e.g., EchA, protein chain elongation factor EF-Ts, 50S ribosomal subunits L7/L12/L32/L29, cysteine synthase A, glycerophosphodiester phosphodiesterase, iron superoxide dismutase). For the TOM-Green/IsoILR1/GSHI system, the expression level of 49 proteins was changed out of 364 identified proteins. The induced proteins due to the addition of TOM-Green, IsoILR1, and GSHI were involved in the oxidative defense mechanism, pyruvate metabolism, and glutathione synthesis (e.g., 30S ribosomal subunit proteins S3 and S16, 50S ribosomal subunit protein L20, alkyl hydroperoxide reductase, lactate dehydrogenase, acetate kinase, cysteine synthase A). Enzymes involved in indole synthesis, fatty acid synthesis, gluconeogenesis, and the tricarboxylic acid cycle were repressed (e.g., tryptophanase, acetyl-CoA carboxylase, phosphoenolpyruvate carboxykinase, malate dehydrogenase). Hence, the metabolic engineering that leads to enhanced aerobic degradation of 1 mM cis-DCE (2.4-4-fold more chloride ions released) and reduced toxicity from cis-DCE epoxide results in enhanced synthesis of glutathione coupled with an induced stress response as well as repression of fatty acid synthesis, gluconeogenesis, and the tricarboxylic acid cycle.
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PMID:Proteome changes after metabolic engineering to enhance aerobic mineralization of cis-1,2-dichloroethylene. 1673 90

Iron is an essential element to support the growth and survival of Trichomonas vaginalis. It plays a critical role in the host-parasite interaction, and modulates the expression of virulence factors in this protozoan. In this work, parasites grown in iron-rich and iron-depleted media were analyzed by (i) light and scanning electron microscopy and (ii) 2-DE and MS. Withdrawal of iron from the culture medium resulted in dramatic changes in both the morphology and in the proteome pattern of T. vaginalis. Trophozoites underwent transformation from ellipsoid or amoeboid forms to rounded cells, whose flagella and axostyle were internalized. Forty-five proteins differentially expressed in parasites cultivated in the absence of iron were identified. In iron-depleted parasites, enzymes involved in energetic metabolism, proteolysis and hydrogenosomal iron-sulfur (Fe-S) proteins were down-regulated or even suppressed. Among up-regulated proteins, six isoforms of actin were detected. In addition, phosphoenolpyruvate carboxykinase, putative lactate dehydrogenase, and putative adenosine triphosphatase were also up-regulated or were exclusively observed in gels related to iron-depleted parasites. Our data demonstrate that iron has a pivotal role in the regulation of the morphological transformation of T. vaginalis and modulates the expression of both Fe-S and non-Fe-S proteins in the parasite.
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PMID:A further proteomic study on the effect of iron in the human pathogen Trichomonas vaginalis. 1751 79


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