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:2.3.3.1 (citrate synthase)
4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pyruvate kinase (EC 2.7.1.40) from Azotobacter vinelandii responds sharply to the adenylate energy charge, with a decrease in activity at high values of charge, as expected for an enzyme of an adenosine triphosphate-regenerating sequence. Glycolytic intermediates, especially glucose 6-phosphate, fructose 6-phosphate, and fructose-1,6-diphosphate, strongly stimulate the reaction and overcome the inhibition caused by high values of energy charge. Thus, the properties of this enzyme depend on interaction between energy charge and the concentrations of hexose phosphates. The properties of pyruvate kinase, together with those of phosphoenolpyruvate carboxylase, aspartokinase, and citrate synthase, seem adapted to provide appropriate partitioning of phosphoenolpyruvate between competing pathways in response to metabolic need.
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PMID:Regulation at the phosphoenolpyruvate branchpoint in Azotobacter vinelandii: pyruvate kinase. 555 41

1. The enzymes in ultrasonically prepared extracts of Chloropseudomonas ethylicum were studied to elucidate how this organism assimilates acetate and carbon dioxide and why it cannot grow with either of these two compounds alone. 2. Such extracts can (i) convert acetate and oxaloacetate into alpha-oxoglutarate, (ii) convert oxaloacetate into succinyl-CoA, (iii) convert phosphopyruvate into 3-phosphoglyceraldehyde and (iv) interconvert phosphopyruvate and pyruvate via oxaloacetate. 3. Pyruvate kinase, alpha-oxoglutarate dehydrogenase, ribulose diphosphate carboxylase, isocitrate lyase and malate synthase were not detected. 4. It is difficult to detect aconitate hydratase, fumarate hydratase and citrate synthase in extracts of the organism ultrasonically treated in tris buffer; to demonstrate these enzymes extracts should be prepared in phosphate buffer containing 2-mercaptoethanol. 5. Provided that this organism can synthesize pyruvate from acetate and carbon dioxide, the enzymes detected are sufficient to account for the nutritional requirements of this organism.
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PMID:The assimilation of carbon by Chloropseudomonas ethylicum. 563 17

The levels of Krebs cycle, glyoxylate cycle, and certain other enzymes were measured in a wild-type strain and in seven groups of acetate-nonutilizing (acu) mutants of Neurospora crassa, both after growth on a medium containing sucrose and after a subsequent 6-hr incubation in a similar medium, containing acetate as the sole source of carbon. In the wild strain, incubation in acetate medium caused a rise in the levels of isocitrate lyase, malate synthase, phosphoenolpyruvate carboxykinase, acetyl-coenzyme A synthetase, nicotinamide adenine dinucleotide phosphate-linked isocitrate dehydrogenase, citrate synthase, and fumarate hydratase. Isocitrate lyase activity was absent in acu-3 mutants; acu-5 mutants lacked acetyl-coenzyme A synthetase activity; and no oxoglutarate dehydrogenase activity (or only low levels) could be detected in acu-2 and acu-7 mutants. In acu-6 mutants, phosphoenolpyruvate carboxykinase activity was either very low or absent. No specific biochemical deficiencies could be attributed to the acu-1 and acu-4 mutations. The role of several of these enzymes during growth on acetate is discussed.
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PMID:Acetate-nonutilizing mutants of Neurospora rassa. II. Biochemical deficiencies and the roles of certain enzymes. 564 48

1. Citrate synthase (EC 4.1.3.7) was purified 750-fold from rat liver. 2. Measurements of the Michaelis constants for the substrates of citrate synthase gave values of 16mum for acetyl-CoA and 2mum for oxaloacetate. Each value is independent of the concentration of the other substrate. 3. The inhibition of citrate synthase by ATP, ADP and AMP is competitive with respect to acetyl-CoA. With respect to oxaloacetate the inhibition by AMP is competitive, but the inhibition by ADP and ATP is mixed, being partially competitive. 4. At low concentrations of both substrates the inhibition by ATP is sigmoidal and a Hill plot exhibits a slope of 2.5. 5. The pH optimum of the enzyme is 8.7, and is not significantly affected by ATP. 6. Mg(2+) inhibits citrate synthase slightly, but relieves the inhibition caused by ATP in a complex manner. 7. At constant total adenine nucleotide concentration made up of various proportions of ATP, ADP and AMP, the activity of citrate synthase is governed by the concentration of the sum of the energy-rich phosphate bonds of ADP and ATP. 8. The sedimentation coefficient of the enzyme, as measured by activity sedimentation, is 6.3s, equivalent to molecular weight 95000.
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PMID:The kinetic properties of citrate synthase from rat liver mitochondria. 582 Jun 45

Use of buffers in homogenization media can result in loss of considerable particulate enzyme activity even with low-speed centrifugation. Addition of tris chloride buffer to 0.25 M sucrose homogenization media resulted in precipitation of 80 to 95% of the activity of two mitochondrial marker enzymes (3-hydroxy-3-methylglutaryl CoA lyase and citrate synthase) with the nuclear fraction during differential centrifugation. Lactate dehydrogenase, a cytoplasmic marker, was not precipitated under the same conditions, indicating that the precipitated enzymes were not associated with intact cells. Photomicrographs showed that tris chloride buffers resulted in mitochondrial aggregation. Isolated mitochondria resuspended in tris chloride or potassium phosphate buffer also aggregated, which resulted in a marked decrease in assayable mitochondrial enzyme activity.
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PMID:Buffer-induced rat liver mitochondrial aggregation during differential centrifugation. 612 25

The degradation of glucose by Trypanosoma cruzi leads to the excretion of succinate. Malate dehydrogenase (MDH) participates in this process by reducing to malate the oxaloacetate synthesized by the glycosomal enzyme, phosphoenolpyruvate carboxykinase. The best coupling for these two sequential reactions would be attained if both enzymes were placed in the same subcellular compartment. The intracellular distribution of the MDH activity in epimastigotes of T. cruzi was studied by two methods. Selective disruption of cellular membranes with increasing concentrations of digitonin, indicated that trypanosomal MDH is particulate. Isopycnic centrifugation in a sucrose gradient of a large granule fraction, obtained by grinding the cells with silicon carbide, showed the presence of two MDH activities: one banding together with the glycosomal marker phosphoenolpyruvate carboxykinase, the other with the mitochondrial marker citrate synthase. Isoelectrofocusing of cell-free extracts led to the separation of two enzyme forms, with pI values of about 3.5 (MDHa) and 9.4 (MDHb). These forms had similar molecular weights (approx. 60 000) and apparent Km values, but showed a small but consistent difference in their pH optima (9.23 for MDHa and 9.05 for MDHb), and in their activation by inorganic phosphate (apparent Ka values of 33 mM and 87 mM, for MDHa and MDHb, respectively). Determination of the pH optima of the enzyme forms separated by isopycnic centrifugation suggests that the glycosomal enzyme form is MDHa, and the mitochondrial one is MDHb.
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PMID:Glycosomal and mitochondrial malate dehydrogenases in epimastigotes of Trypanosoma cruzi. 637 51

The compartimentation and the relative strength of binding of the enzymes lipoamide dehydrogenase (LIPDH), citrate synthase (CS), and beta-hydroxyacyl-coenzyme A-dehydrogenase (HADH) in mitochondria isolated from bovine muscle (M. sternomandibularis) were studied using the following methods: Availability of the enzymes for proteases before and after opening of the intracrystal line space and after disintegration of the mitochondrial membranes; release of the enzymes after different treatments of the mitochondria: homogenization with phosphate buffer plus Triton X-100; suspension in dest. water and saccharose-tris buffer with and without added digitonin; ultrasonic treatment; freezing and thawing. From the results it can be concluded that the three enzymes are bound to the inner surface of the inner membrane of the mitochondrion, and that the binding strength increases according to the series CS less than HADH less than LIPDH.
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PMID:[Lipoamide dehydrogenase, citrate synthase and beta-hydroxyacyl-CoA-dehydrogenase of skeletal muscle. II. Compartmentalization of the enzymes in muscle mitochondria and their relative binding capacity]. 638 Jan 31

A new, weakly hydrophobic, high-performance liquid chromatography column has been developed for the separation of native proteins based on their relative hydrophobicities. Starting with a covalently bound, hydrophilic polyamine matrix, packing materials were synthesized through acylation with anhydrides and acid chlorides of increasing chain length to obtain increasingly hydrophobic surfaces. Proteins in aqueous buffers were induced to bind hydrophobically to the columns by the use of high salt concentrations in the mobile phase. Elution was achieved by decreasing the ionic strength of the solvent in a linear gradient. A mixture of cytochrome c, conalbumin, and beta-glucosidase was used as a standard to test the resolving power of newly synthesized columns. On a 4-cm butyrate column, baseline resolution was achieved in 20 min with a gradient of 3.0 mu sodium sulfate in 0.1 M potassium phosphate buffer, pH 7.0, to water. The static loading capacity for each column was determined using a hemoglobin binding assay. Capacities normally ranged between 150 and 180 mg of hemoglobin per gram of support. Since proteins are not denatured in hydrophobic interaction chromatography, enzymes eluted from the column retained enzymatic activity. Samples of alpha-amylase and beta-glucosidase ranging in size from 10 to 200 micrograms were recovered from the butyrate column with greater than 92% enzymatic activity in all cases. In a single trial, the enzyme citrate synthase was recovered from the benzoate column with 92% retention of enzymatic activity.
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PMID:High-performance hydrophobic interaction chromatography of proteins. 642 67

In aggregates of nervous tissue, cultivated for 1--7 days at 0 degree C and 37 degrees C, respectively, the activities of seven enzymes of energy liberating metabolism were estimated, in order to evaluate their metabolic "profiles" and changes during cultivation. The enzymes used as markers of different pathways of energy liberation from substrates were: lactate dehydrogenase - LDH - (EC 1.1.1.27), triose-3-phosphate dehydrogenase - TPDH - (EC 1.2.1.12), glycerol-3-phosphate dehydrogenase - GPDH - (EC 1.1.1.8), hexokinase - HK - (EC 2.7.1.1.), malate:NAD dehydrogenase - MDH - (EC 1.1.1.37), citrate synthase - CS - (EC 4.1.3.7), and 3-hydroxyacetyl CoA dehydrogenase - HOADH - (EC 1.1.1.35). During the cultivation, some changes in the metabolic "profiles" were observed. Although some of these changes as well as the differences between the cultivation at 0 degree C and 37 degrees C, were statistically significant, they were not greater than the variations between different samples of any tissue taken at different times. They were not, therefore considered to be of major significance. However, all the aggregates exhibited "profiles" characteristic for the nervous tissue, with relatively very high activity of HK, high activity of MDH and CS (carbohydrate breakdown) and low activity of GPDH and HOADH (lipid catabolism).
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PMID:Enzyme activity pattern in developing mouse brain in situ in embryonic brain aggregated cells at 37 degrees C and 0 degree C. 661 8

Biopsies from 15 human gliomas, five meningiomas, four Schwannomas, one medulloblastoma, and four normal brain areas were analyzed for 12 enzymes of energy metabolism and 12 related metabolites and cofactors. Samples, 0.01-0.25 microgram dry weight, were dissected from freeze-dried microtome sections to permit all the assays on a given specimen to be made, as far as possible, on nonnecrotic pure tumor tissue from the same region. Great diversity was found with regard to both enzyme activities and metabolite levels among individual tumors, but the following generalities can be made. Activities of hexokinase, phosphorylase, phosphofructokinase, glycerophosphate dehydrogenase, citrate synthase, and malate dehydrogenase levels were usually lower than in brain; glycogen synthase and glucose-6-phosphate dehydrogenase were usually higher; and the averages for pyruvate kinase, lactate dehydrogenase, 6-phosphogluconate dehydrogenase, and beta-hydroxyacyl coenzyme A dehydrogenase were not greatly different from brain. Levels of eight of the 12 enzymes were distinctly lower among the Schwannomas than in the other two groups. Average levels of glucose-6-phosphate, lactate, pyruvate, and uridine diphosphoglucose were more than twice those of brain; 6-phosphogluconate and citrate were about 70% higher than in brain; glucose, glycogen, glycerol-1-phosphate, and malate averages ranged from 104% to 127% of brain; and fructose-1,6-bisphosphate and glucose-1,6-bisphosphate levels were on the average 50% and 70% those of brain, respectively.
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PMID:Diversity of metabolic patterns in human brain tumors: enzymes of energy metabolism and related metabolites and cofactors. 661 61


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