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)

Citric acid secretion by fluorescent pseudomonads has a distinct significance in microbial phosphate solubilization. The role of citrate synthase in citric acid biosynthesis and glucose catabolism in pseudomonads was investigated by overexpressing the Escherichia coli citrate synthase (gltA) gene in Pseudomonas fluorescens ATCC 13525. The resultant approximately 2-fold increase in citrate synthase activity in the gltA-overexpressing strain Pf(pAB7) enhanced the intracellular and extracellular citric acid yields during the stationary phase, by about 2- and 26-fold, respectively, as compared to the control, without affecting the growth rate, glucose depletion rate or biomass yield. Decreased glucose consumption was paralleled by increased gluconic acid production due to an increase in glucose dehydrogenase activity. While the extracellular acetic acid yield increased in Pf(pAB7), pyruvic acid secretion decreased, correlating with an increase in pyruvate carboxylase activity and suggesting an increased demand for the anabolic precursor oxaloacetate. Activities of two other key enzymes, glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase, remained unaltered, and the contribution of phosphoenolpyruvate carboxylase and isocitrate lyase to glucose catabolism was negligible. Strain Pf(pAB7) demonstrated an enhanced phosphate-solubilizing ability compared to the control. Co-expression of the Synechococcus elongatus PCC 6301 phosphoenolpyruvate carboxylase and E. coli gltA genes in P. fluorescens ATCC 13525, so as to supplement oxaloacetate for citrate biosynthesis, neither significantly affected citrate biosynthesis nor caused any change in the other physiological and biochemical parameters measured, despite approximately 1.3- and 5-fold increases in citrate synthase and phosphoenolpyruvate carboxylase activities, respectively. Thus, our results demonstrate that citrate synthase is rate-limiting in enhancing citrate biosynthesis in P. fluorescens ATCC 13525. Significantly low extracellular citrate levels as compared to the intracellular levels in Pf(pAB7) suggested a probable limitation of efficient citrate transport.
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PMID:Enhanced citric acid biosynthesis in Pseudomonas fluorescens ATCC 13525 by overexpression of the Escherichia coli citrate synthase gene. 1944 43

Carbon dioxide has been known for some time to be one of the products of carbohydrate metabolism. More recently it has been demonstrated that CO2 is utilized in pathways of carbohydrate synthesis. Five reactions have been described by which CO2 is incorporated into citric acid intermediates. Two important functions of CO2 fixation reactions have been suggested. Citric acid cycle intermediates can be generated by the fixation reactions and schemes utilizing two of the reaction will reverse the pyruvic kinase reaction. The latter is a step essential to glucogenesis. This paper shows that carbon dioxide fixation occurs in rat skin. The labeling pattern of oxaloacetate after fixation is consistent with patterns predicted by either the malic enzyme or propionyl carboxylase fixation reactions. The presence of the phosphopyruvic carboxykinase and pyruvic carboxylase reactions cannot be definitely ruled out by the experimental data. More work on the enzymatic level should show the significance of these various fixaon reactions in skin. Further experiments may also elucidate a relationship between factors known to affect the fixation reactions which also produce gross and microscopic changes in skin.
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PMID:Carbon dioxide fixation in skin. 2562 43