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 test model of studying the effects of chronic pharmacological treatment on cerebral metabolism related to energy transduction was developed. The most useful biochemical parameters were the cerebral enzymatic activities related to the glycolytic pathway (lactate dehydrogenase), the Krebs' cycle (citrate synthetase and malate dehydrogenase) and the electron transfer chain (total NADH-cytochrome c reductase and cytochrome oxidase). The model is based on the natural growth-dependent changes occurring in the rat during aging (from 10 to 60 weeks of life). As test drug, 10-methoxy-1,6-dimethyl-ergoline-8 beta-methanol-(5-bromonicotinate) (nicergoline, Sermion) was administered daily for three periods of 16 weeks each (10-26, or 28-44, or 44-60 weeks of life) by two different administration routes (oral and i.p.), and at two different dose levels: oral 1 or 4, i.p. 0.25 or 1 mg/kg. Biochemical data were obtained blindly after 4, 8, 12 and 16 weeks of treatment. The drug tested exerted different effects which were dependent on the various administration periods and the administration routes. No dose-effect relationship was established.
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PMID:[Cerebral enzymatic activities related to energy transduction processes. A model for the evaluation of pharmacological changes in the brain of the adult rat]. 54 66

The activity of enzymes involved in carbon metabolism of Candida boidinii KDI was compared on media containing methanol with bicarbonate and without it. The presence of carbon dioxide stimulated the activity of methanol oxidase, formaldehyde dehydrogenase, hexulose phosphate synthase and particularly carboxylases of pyruvate and phosphoenol pyruvate. At the same time, the activity of formate dehydrogenase, citrate synthase and isocitrate lyase decreased. Therefore, carbon dioxide produces a significant effect on methylotrophic metabolism of Candida boidinii KDI and is actively involved in biosynthetic processes.
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PMID:[Effect of carbon dioxide on the methylotrophic metabolism of Candida boidinii]. 71 85

Considered are our own data and those found in literature on the properties of yeast mutants impaired in their ability to utilize methanol as sole carbon and energy source; hypotheses about the role of alcohol oxidase and citrate synthase in biogenesis of peroxisomes are proposed. It has been proved that formaldehyde reductase participates in the control of the formaldehyde level in the cell. Properties of mutants defective in the catabolite repression and inactivation of enzymes of methanol metabolism are described. The existence of several autonomous mechanisms of the catabolite repression of alcohol oxidase has been shown. It has been found, that the induction of glyoxysomal enzymes of C2-metabolism is repressed by methanol in the ecr1 mutant of Pichia pinus with the affected repression of alcohol oxidase by ethanol. Data are presented on the regulatory properties of the recently discovered acidification system of the medium induced by methanol. Such acidification occurs due to symport extrusion of protons and formate anions from the cells.
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PMID:Genetic control of methanol utilization in yeasts. 306 50

The enzymes beta-ketothiolase and citrate synthase from the facultatively methylotrophic Methylobacterium rhodesianum MB 126, which uses the serine pathway, were purified and characterized. The beta-ketothiolase had a relatively high Km for acetyl-CoA (0.5 mM) and was strongly inhibited by CoA (Ki 0.02 mM). The citrate synthase had a much higher affinity for acetyl-CoA (Km 0.07 mM) and was significantly inhibited by NADH (Ki 0.15 mM). The intracellular concentration of CoA metabolites and nucleotides was determined in M. rhodesianum MB 126 during growth on methanol. The level of CoA decreased from about 0.6 nmol (mg dry mass)-1 during growth to the detection limit when poly(beta-hydroxybutyrate) (PHB) accumulated. Nearly unchanged intracellular concentrations of NADH, NADPH, and acetyl-CoA of about 0.5, 0.6-0.7, and 1.0 nmol (mg dry mass)-1, respectively, were determined during growth and PHB synthesis. During growth, the beta-ketothiolase was almost completely inhibited by CoA, and acetyl-CoA was principally consumed by the citrate synthase. During PHB accumulation, the beta-ketothiolase had about 75% of its maximum activity and showed much higher activity than citrate synthase, which at the actual NADH concentration was about 75% inhibited. NADPH concentration was sufficiently high to allow the unlimited activity of acetoacetyl-CoA reductase (Km NADPH 18 microM). PHB synthesis is probably mainly controlled by the CoA concentration in M. rhodesianum MB 126.
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PMID:Competition between beta-ketothiolase and citrate synthase during poly(beta-hydroxybutyrate) synthesis in Methylobacterium rhodesianum. 908 18

The intracellular concentration of CoA metabolites and nucleotides was determined in batch cultures of Methylobacterium rhodesianum grown on methanol and shifted to growth on fructose. The intracellular concentration of CoA decreased from a high value of 0.6 nmol/mg poly(beta-hydroxybutyrate)-free bacterial dry mass during growth on methanol to a low value of 0.03 nmol/mg poly(beta-hydroxybutyrate)-free bacterial dry mass after a shift to fructose as a carbon source. The levels of NADH, NADPH, and acetyl-CoA were also lower. Under these conditions, acetyl-CoA was metabolized by both citrate synthase and beta-ketothiolase, and poly(beta-hydroxybutyrate) synthesis and growth occurred simultaneously during growth on fructose. Moreover, the level of ATP was approximately 50% lower during growth on fructose, supporting the hypothesis of a bottleneck in the energy supply during the growth of M. rhodesianum with fructose.
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PMID:Regulation of poly(beta-hydroxybutyrate) synthesis in Methylobacterium rhodesianum MB 126 growing on methanol or fructose. 953 38

A stoichiometric model of central metabolism was developed based on new information regarding metabolism in this bacterium to evaluate the steady-state growth capabilities of the serine cycle facultative methylotroph Methylobacterium extorquens AM1 during growth on methanol, succinate, and pyruvate. The model incorporates 20 reversible and 47 irreversible reactions, 65 intracellular metabolites, and experimentally-determined biomass composition. The flux space for this underdetermined system of equations was defined by finding the elementary modes, and constraints based on experimental observations were applied to determine which of these elementary modes give a reasonable description of the flux distribution for each growth substrate. The predicted biomass yield, on a carbon atom basis, is 49.8%, which agrees well with the range of published experimental yield measurements (37-50%). The model predicts the cell to be limited by reduced pyridine nucleotide availability during methylotrophic growth, but energy-limited when growing on multicarbon substrates. Mutation and phenotypic analysis was used to explore a previously unknown region of the metabolic map and to confirm the stoichiometry of the pathways in this region used in the metabolic model. Based on genome sequence data and simulation results, three enzymes involved in C(3)-C(4) interconversion pathways were predicted to be mutually redundant: malic enzyme, phosphoenolpyruvate carboxykinase, and phosphoenolpyruvate synthase. Insertion mutations in the genes predicted to encode these enzymes were made and these mutants were capable of growing on all substrates tested, confirming the redundancy of these pathways. Likewise, pathway analysis suggests that the TCA cycle enzymes citrate synthase and succinate dehydrogenase are essential for all growth substrates. In keeping with these predictions, null mutants could not be obtained in these genes. Finally, a similar model was developed for the ribulose monophosphate pathway obligate methylotroph Methylobacillus flagellatum KT to compare the efficiency of carbon utilization in the two types of methylotrophic carbon utilization pathways. The predicted yield for this organism on methanol is 65.9%.
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PMID:Stoichiometric model for evaluating the metabolic capabilities of the facultative methylotroph Methylobacterium extorquens AM1, with application to reconstruction of C(3) and C(4) metabolism. 1192 Apr 46

The thermotolerant, restrictive methylotroph Bacillus methanolicus MGA3 (ATCC 53907) can secrete 55 g of glutamate per liter (maximum yield, 0.36 g/g) at 50 degrees C with methanol as a carbon source and a source of ammonia in fed-batch bioreactors. A homoserine dehydrogenase mutant, 13A52-8A66, secreting up to 35 g of L-lysine per liter in fed-batch fermentations had minimal 2-oxoglutarate dehydrogenase activity [7.3 nmol min(-1) (mg of protein)(-1)], threefold-increased pyruvate carboxylase activity [535 nmol min(-1) (mg of protein)(-1)], and elevated citrate synthase (CS) activity [292 nmol min(-1) (mg of protein)(-1)] and simultaneously secreted glutamate (20 to 30 g per liter) and L-lysine. The flow of carbon from oxaloacetate is split between transamination to aspartate and formation of citrate. To investigate the regulation of this branch point, the B. methanolicus gene citY encoding a CSII protein with activity at 50 degrees C was cloned from 13A52-8A66 into a CS-deficient Escherichia coli K2-1-4 strain. A citY-deficient B. methanolicus mutant, NCS-L-7, was also isolated from the parent strain of 13A52-8A66 by N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis, followed by selection with monofluoroacetate disks on glutamate plates. Characterization of these strains confirmed that citY in strain 13A52-8A66 was not altered and that B. methanolicus possessed several forms of CS. Analysis of citY cloned from NCS-L-7 showed that the reduced CS activity resulted from a frameshift mutation. The level of glutamate secreted by NCS-L-7 was reduced sevenfold and the ratio of L-lysine to glutamate secreted was increased 4.5-fold compared to the wild type in fed-batch cultures with glutamate feeding. This indicates that glutamate secretion in L-lysine-overproducing mutants can be altered in favor of increased L-lysine secretion by regulating in vivo CS activity.
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PMID:Role of the Bacillus methanolicus citrate synthase II gene, citY, in regulating the secretion of glutamate in L-lysine-secreting mutants. 1283 72

Molecular chaperones play a central role in maintaining protein structure within a cell. Previously, we determined that the gene encoding a molecular chaperone, a thermosome, from the hyperthermophilic archaeon Methanocaldococcus jannaschii is upregulated upon lethal heat shock. We have recombinantly expressed this thermosome (rTHS) and show here that it is both stable and fully functional in aqueous solutions containing water-miscible organic co-solvents. Based on circular dichroism the secondary structure of rTHS was not affected by one-hour exposures to a variety of co-solvents including 30% v/v acetonitrile (ACN) and 50% methanol (MeOH). By contrast, the secondary structure of a mesophilic homologue, GroEL/GroES (GroE), was substantially disrupted. rTHS reduced the aggregation of ovalbumin and citrate synthase in 30% ACN, assisted refolding of citrate synthase upon solvent-inactivation, and stabilized citrate synthase and glutamate dehydrogenase in the direct presence of co-solvents. Apparent total turnover numbers of these enzymes in denaturing solutions increased by up to 2.5-fold in the presence of rTHS. Mechanistic models are proposed to help ascertain specific conditions that could enhance or limit organic solvent-induced chaperone activity. These models suggest that thermodynamic stability and the reversibility of enzyme unfolding play key roles in the effectiveness of enzyme recovery by rTHS.
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PMID:Chaperone function in organic co-solvents: experimental characterization and modeling of a hyperthermophilic chaperone subunit from Methanocaldococcus jannaschii. 1815 40

Methanococcoides burtonii is a cold-adapted methanogenic archaeon from Ace Lake in Antarctica. Methanol and methylamines are the only substrates it can use for carbon and energy. We carried out quantitative proteomics using iTRAQ of M. burtonii cells grown on different substrates (methanol in defined media or trimethylamine in complex media), using techniques that enriched for secreted and membrane proteins in addition to cytoplasmic proteins. By integrating proteomic data with the complete, manually annotated genome sequence of M. burtonii, we were able to gain new insight into methylotrophic metabolism and the effects of methanol on the cell. Metabolic processing of methanol and methylamines is initiated by methyltransferases specific for each substrate, with multiple paralogs for each of the methyltransferases (similar to other members of the Methanosarcinaceae). In M. burtonii, most methyltransferases appear to have distinct roles in the metabolism of methylated substrates, although two methylamine methyltransferases appear to be nonfunctional. One set of methyltransferases for trimethylamine catabolism appears to be membrane associated, potentially providing a mechanism to directly couple trimethylamine uptake to demethylation. Important roles were highlighted for citrate synthase, glutamine synthetase, acetyl-CoA decarbonylase/synthase, and pyruvate synthase in carbon and nitrogen metabolism during growth on methanol. M. burtonii had only a marginal response to the provision of exogenous amino acids (from yeast extract), indicating that it is predisposed to the endogenous synthesis of amino acids. Growth on methanol appeared to cause oxidative stress in the cell, possibly through the formation of reactive nonoxygen species and formaldehyde, and the oxidative inactivation of corrinoid proteins, with the cell responding by elevating the synthesis of universal stress (Usp) proteins, several nucleic acid binding proteins, and a serpin. In addition, changes in levels of cell envelope proteins were linked to counteracting the disruptive solvent effects of methanol on cell membranes. This is the first global proteomic study to examine the effects of different carbon sources on the growth of an obligately methylotrophic methanogen.
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PMID:Global proteomic analysis of the insoluble, soluble, and supernatant fractions of the psychrophilic archaeon Methanococcoides burtonii. Part II: the effect of different methylated growth substrates. 1994 65