Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A gene encoding 544 amino acids for a subunit of group II chaperonin (thermosome) was cloned from a thermophilic methanogen, Methanococcus thermolithotrophicus. The deduced amino acid sequence showed 66.5, 56.1, and 20.1% similarities to those of Methanopyrus kandleri and Thermoplasma acidophilum and group I chaperonin of Escherichia coli, respectively. We call this chaperonin MTTS (M. thermolithotrophicus thermosome). The MTTS gene was expressed in E. coli. The purified recombinant MTTS seemed to be monomeric on gel filtration in the absence of Mg2+ and ATP. The monomer assembled to an oligomer (complex) in the presence of 50 mM MgCl2, 0.25 mM ATP, and 0.3 M (NH4)2SO4. It was eluted immediately before the elution volume of E. coli GroEL tetradecamer on gel filtration with a TSKgel G3000SWXL column. This reconstructed MTTS complex showed the cylindrical structure with two stacked rings in electron microscopy. The MTTS complex formed filamentous structures in the presence of Mg2+ and ATP at the protein concentration above 3.0 mg/ml. This filament formation was reversible. The MTTS filament was dissociated to the complex by dilution to the protein concentration of 0.2 mg/ml, even in the presence of Mg2+ and ATP. The MTTS complex exhibited weak ATPase activity with the hydrolysis rate of 74 mol of ATP hydrolysis/mol of MTTS complex/min at 70 degreesC. The MTTS complex promoted the refolding of chemically denatured thermophilic archaeal citrate synthase and glucose dehydrogenase at 50 degreesC in an ATP-dependent fashion. The analysis of nucleotide specificity of chaperone activity of MTTS suggested that it was coupled with hydrolysis of ATP, CTP, or UTP.
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PMID:Group II chaperonin in a thermophilic methanogen, Methanococcus thermolithotrophicus. Chaperone activity and filament-forming ability. 977 67

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

Genetic engineering of fluorescent pseudomonads for various industrially, agriculturally and environmentally important bioprocesses often involves the use of suitable plasmids. Plasmid-mediated alterations in host physiology and metabolism are poorly understood for this group of organisms. Thus, we investigated the metabolic perturbations in Pseudomonas fluorescens 13525 due to the independent and combined presence of broad-host-range plasmids, pBBR1MCS-2 (copy number 30) and pUCPM18 derived pAB4 and pAB8 (copy number 14-16). Presence of pAB4 and pAB8 not only significantly increased the growth rate and glucose utilization of P. fluorescens 13525, but also increased glucose dehydrogenase activity and gluconic acid production indicating enhanced direct oxidative pathway for glucose catabolism. Additionally, increased secretion of pyruvic, acetic, and citric acids caused faster media acidification in presence of pAB4 and pAB8. Simultaneous presence of pAB4/pAB8 in Pf (pAB48) and pAB4/pBBR1MCS-2 in Pf (pAB4BBR1MCS-2) reduced their respective copy numbers to nearly half. Pf (pAB48) demonstrated further increase in direct oxidation pathway without altering growth and glucose depletion rates, as compared with single transformants. Conversely, pBBR1MCS-2 plasmid did not greatly alter P. fluorescens 13525 metabolism when present independently but masked the effects imposed by pAB4 when present in its combination. In conclusion, P. fluorescens 13525 redesigns its metabolism in response to the presence of plasmids irrespective of their nature, by enhancing anaplerosis with a simultaneous reduction in catabolism as indicated by increased pyruvate carboxylase and decreased citrate synthase activities, respectively. Such information will be helpful for vector designing during genetic engineering of fluorescent pseudomonads.
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PMID:Broad-host-range plasmid-mediated metabolic perturbations in Pseudomonas fluorescens 13525. 2057 95