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)

Soluble bifunctional enzyme aggregates have been prepared by cross-linking the sequential enzymes malate dehydrogenase (EC 1.1.1.37) and citrate synthase (EC 4.1.3.7) using glutaraldehyde. The kinetic behaviour of this two-enzyme system in its aggregated and non-aggregated form was studied both in free solution and immobilized on Sepharose beads. This study was undertaken in order to distinguish between the following two factors which may account for the increased efficiency found in general in co-immobilized consecutive two-enzyme systems: (a) closer proximity between the participating enzymes and (b) establishment of a favourable microenvironment (such as higher local intermediate concentration caused by increased diffusional hindrance in the gel phase). It was found that in spite of a reduction of the distance between the two enzymes in the aggregated form by an estimated factor of 10(3), no kinetic advantage (shorter lag phase or higher steady-state rate) could be detected compared to the corresponding system with the two enzymes not linked to each other. However, both systems immobilized to Sepharose reached the steady-state rate of citrate formation almost immediately, in contrast to the corresponding free systems which exhibited pronounced lag phase. These results indicate that, at least in the above systems and under the conditions given, diffusional hindrance in the gel phase of the intermediate oxaloacetate, which is present in rate-limiting concentrations, is the dominant cause of the observed higher efficiency in immobilized systems.
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PMID:Aspects of microenvironmental compartmentation. An evaluation of the influence of restricted diffusion, exclusion effects, and enzyme proximity on the overall efficiency of the sequential two-enzyme system malate dehydrogenase--citrate synthase in its soluble and immobilized form. 59 Feb 71

Rats were treated by daily alprenolol (10, 20 and 50 mg/kg) injections for 5 days a week for 4 weeks. At 20--21 degrees C alprenolol treatment retarded the weight gain of the animals and increased the weight of the adrenals. These changes were not seen at 29 degrees C. The reduction in size and fat content of the interscapular brovin adipose tissue in drug-treated rats was independent of experimental temperature. At 20--21 degrees C prolonged beta-blockade did not cause any changes in the enzymes of the energy metabolism. At 29 degrees C, however, alprenolol treatment antagonized the decrease in activity of oxidative enzymes (succinate dehydrogenase, malate dehydrogenase, citrate synthase) and the decrease in protein concentration of the cardiac muscle. In skeletal muscle alprenolol treatment significantly decreased the activities of oxidative enzymes and antagonized the rise in the activity of lactate dehydrogenase resulting from warm acclimation. The increased activities of oxidative enzymes in interscapular brown adipose tissue of aprenolol treated rats were coupled with an increase in protein concentration of the tissue. Although these changes were more marked at 29 degree C they were observable at 20--21 degree C, too. The difference in the drug effects at 20--21 degrees C and 29 degrees C can be accounted for by the compensatory catecholamine release at the lower temperature, due to impaired thermoregulatory capacity after alprenolol. Prolonged beta blockade decreased the exercise tolerance and cold tolerance of the rats. An increased response of the diastolic blood pressure to an alpha-adrenergic drug, noradrenaline, and a decreased response to a beta-adrenergic drug, isoprenaline, in alprenolol-treated rats indicates a shift from beta- to alpha-receptors.
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PMID:Effect of prolonged beta-blockade on energy metabolism and adrenergic responses in the rat. 59 3

The pathway of acetate assimilation in Methanosarcina barkeri was determined from analysis of the position of label in alanine, aspartate, and glutamate formed in cells grown in the presence of [14C]acetate and by measurement of enzyme activities in cell extracts. The specific radioactivity of glutamate from cells grown on [1-14C]- or [2-14C]acetate was approximately twice that of aspartate. The methyl and carboxyl carbons of acetate were incorporated into aspartate and glutamate to similar extents. Degradation studies revealed that acetate was not significantly incorporated into the C1 of alanine, C1 or C4 of aspartate, or C1 of glutamate. The C5 of glutamate, however, was partially derived from the carboxyl carbon of acetate. Cell extracts were found to contain the following enzyme activities, in nanomoles per minute per milligram of protein at 37 degrees C: F420-linked pyruvate synthase, 170; citrate synthase, 0.7; aconitase, 55; oxidized nicotinamide adenine dinucleotide phosphate-linked isocitrate dehydrogenase, 75; and oxidized nicotinamide adenine dinucleotide-linked malate dehydrogenase, 76. The results indicate that M. barkeri assimilates acetate into alanine and aspartate via pyruvate and oxaloacetate and into glutamate via citrate, isocitrate, and alpha-ketoglutarate. The data reveal differences in the metabolism of M. barkeri and Methanobacterium thermoautotrophicum and similarities in the assimilation of acetate between M. barkeri and other anaerobic bacteria, such as Clostridium kluyveri.
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PMID:Acetate assimilation pathway of Methanosarcina barkeri. 76 16

Cell-free extracts of Rickettsia typhi were tested for activities of enzymes of the tricarboxylic acid cycle, of glutamate catabolism, and of glycolysis. The organisms were grown in the yolk sacs of chicken embryos, harvested shortly before the time of embryo death, purified by Renografin density gradient centrifugation, and ruptured in a French pressure cell. The following enzymatic activities were demonstrated: high levels of malate dehydrogenase (MDH), moderate levels of glutamate-oxaloacetate transaminase, glutamate, succinate, and isocitrate dehydrogenases, and citrate synthase, and low levels of glutamate-pyruvate transaminase. The specific activities of some of these enzymes were higher when the rickettsiae were harvested at a time of active proliferation, 3 to 4 days prior to embryo death. Rickettsial MDH was differentiated from host MDH by its migration pattern on polyacrylamide gel electrophoresis. The activities of MDH and two other dehydrogenases, demonstrable after the cells had been disrupted, were absent from purified, intact rickettsial preparations. No activity was detected for glucose-6-phosphate, 6-phosphogluconate, glyceraldehyde-3-phosphate, lactate dehydrogenases, phosphoglucose isomerase, fructoaldolase, or pyruvate kinase. Our results suggest that extracts of R. typhi that contain demonstrable enzymes involved in the catabolism of glutamate and tricarboxylic acid cycle intermediates, unlike Coxiella burnetti, lack detectable glycolytic activity.
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PMID:Enzymatic activities of cell-free extracts of Rickettsia typhi. 82 Jun 44

Tricarboyxlic acid cycle activity was examined in Neisseria gonorrhoeae CS-7. The catabolism of glucose in N. gonorrheae by a combination of the Entner-Doudoroff and pentose phosphate pathways resulted in the accumulation of acetate, which was not further catabolized until the glucose was depleted or growth became limiting. Radiorespirometric studies revealed that the label in the 1 position of acetate was converted to CO2 at twice the rate of the label in the 2 position, indicating the presence of a tricarboxylic acid cycle. Growth on glucose markedly reduced the levels of all tricarboxylic acid cycle enzymes except citrate synthase (EC 4.1.3.7). Extracts of glucose-grown cells contained detectable levels of all tricarboxylic acid cycle enzymes except aconitase (EC 4.2.1.3), isocitrate dehydrogenase (EC 1.1.1.42), and a pyridine nucleotide-dependent malate dehydrogenase (EC 1.1.1.37). Extracts of cells capable of oxidizing acetate lacked only the pyridine nucleotide-dependent malate dehydrogenase. In lieu of this enzyem, a particulate pyridine nucleotide-independent malate oxidase (EC 1.1.3.3) was present. This enzyme required flavin adenine dinucleotide for activity and appeared to be associated with the electron transport chain. Radiorespirometric studies utilizing labeled glutamate demonstrated that a portion of the tricarboxylic acid cycle functioned during glucose catabolism. In spite of the presence of all tricarboxylic acid cycle enzymes, N. gonorrhoeae CS-7 was unable to grow in medium supplemented with cycle intermediates.
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PMID:Physiology and metabolism of pathogenic neisseria: tricarboxylic acid cycle activity in Neisseria gonorrhoeae. 82 68

Microbodies appearing abundantly in n-alkane-grown cells of Candida tropicalis pK 233 were isolated by means of sucrose density gradient centrifugation. Electron microscopical observation showed that the microbodies isolated were intact. Localization of catalase and D-amino acid oxidase in the isolated microbodies was confirmed. Isocitrate lyase, melate synthase and NADP-linked isocitrate dehydrogenase were also located in the microbody, but malate dehydrogenase, citrate synthase, aconitase and NAD-linked isocitrate dehydrogenase were not. Neither cytochrome P-450 not NADPH-cytochrome c reductase, the components involved in the n-alkane hydroxylation system of the yeast, were detected in the microbody fraction.
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PMID:Microbody of n-alkane-grown yeast. Enzyme localization in the isolated microbody. 84 63

In biopsy samples of the lateral part of the quadriceps femoris muscle of 6 obese diabetic male patients and of 11 obese males with a normal glucose tolerance, the activities of 7 enzymes of energy metabolism were estimated: hexokinase, cytoplasmic glycerol-3-phosphate: NAD dehydrogenase, triosephosphate dehydrogenase, lactate dehydrogenase, citrate synthase, malate dehydrogenase and 3-hydroxyacyl-CoA dehydrogenase. The obese diabetic male patients exhibited decreased activities of enzymes of carbohydrate breakdown and cytoplasmic NAD regeneration. Enzymes connected functionally with aerobic metabolism were less affected. The unchanged activity of 3-hydroxyacyl-CoA dehydrogenase points to an increased role of fatty acid catabolism in the muscle.
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PMID:Enzyme activities in quadriceps femoris muscle of obese diabetic male patients. 90 76

1. In 3 groups of men, differing as to the amount and intensity of physical training loads, increasing in the order "sedentary": "sporting": "athletic", enzyme activities were estimated in biopsy samples of m. quadriceps femoris (vastus lateralis). The enzymes were: Hexokinase (HK), NAD: glycerol-3-phosphate dehydrogenase (GPDH), triosephosphate dehydrogenase (TPDH), lactate dehydrogenase (LDH), citrate synthase (CS), NAD: malate dehydrogenase (MDH), and 3-hydroxyacyl-CoA dehydrogenase (HOADH). Indicators of laboratory performance and whole-body metabolic capacities (maximal oxygen consumption etc.) were estimated in the "sporting" and "athletic" groups. 2. In the 2 latter groups, distinguished by greater physical activity, the atypical enzyme activity pattern, remarkable by a low activity of LDH and high relative activities of GPDH and HK, as reported earlier in a sedentary group (Bass et al., 1975a), disappeared. The possibility of the atypical low LDH enzyme activity pattern as resulting from lack of bodily exertion is discussed. 3. The moderately trained "sporting" group distinguishes itself from the "sedentary" one mainly by a higher activity of LDH and by lower activities of GPDH and MDH. In the intensively trained "athletic" group, enzymes connected to aerobic oxidation (MDH, CS, HOADH) and GPDH also show higher activities than in the "sporting" group. The difference between the two more active groups is further borne out by a higher maximum oxygen uptake and carbon dioxide release of the well-trained "athletic" group. This difference of enzyme activity pattern may not be confined to the quadriceps femoris muscle.
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PMID:Enzyme activity patterns of energy supplying metabolism in the quadriceps femoris muscle (vastus lateralis): sedentary men and physically active men of different performance levels. 94 91

The occurrence and levels of activity of various enzymes of carbohydrate catabolism in culture forms (promastigotes) of 4 human species of Leishmania (L. brasiliensis, L. donovani, L. mexicana, and L. tropica) were compared. These organisms possess enzymes of the Embden-Meyerhof pathway but lack lactate dehydrogenase. No evidence could be found for the production of lactic acid by growing cultures and lactic acid could not be detected either in cell-free preparations or after incubation of cell-free extracts with pyruvate and NADH under appropriate conditions. All 4 species possess alpha-glycerophosphate dehydrogenase and alpha-glycerophosphate phosphatase which together could regenerate NAD, thus compensating for the absence of lactate dehydrogenase. The oxidative and nonoxidative reactions of the hexose monophosphate pathway are present in all 4 species. Cell-free extracts have pyruvate dehydrogenase activity which allows the entry of pyruvate into and its subsequent oxidation through the tricarboxylic acid cycle. All enzymes of this cycle, including a thiamine pyrophosphate dependent alpha-ketoglutarate dehydrogenase, are present. Both NAD and NADP-linked malate dehydrogenase activities are present. The isocitrate dehydrogenase is NADP specific. There is an active glutamate dehydrogenase which could compete with alpha-ketoglutarate dehydrogenase for the common substrate (alpha-ketoglutarate). Replenishment of C4 acids is accomplished by heterotrophic CO2 fixation catalyzed by pyruvate carboxylase. All 4 species have high levels of NADH oxidase activity. Several enzymes thus far not found in any species of Leishmania have been demonstrated. These are: phosphoglucose isomerase, triose phosphate isomerase, fructose-1, 6-diphosphatase, 3-phosphoglycerate kinase, enolase, alpha-glycerophosphate dehydrogenase, alpha-glycerophosphate phosphatase, pyruvate dehydrogenase complex, citrate synthase, aconitase, alpha-ketoglutarate dehydrogenase, glutamate dehydrogenase, and NADH oxidase.
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PMID:Enzymes of carbohydrate metabolism in four human species of Leishmania: a comparative survey. 100 46

In the quadriceps femoris muscle of obese women the glycogen concentration was significantly lower than in the control group, while protein and DNA values showed no significant differences. After 37 days of intermittent fasting, which consisted of repeated 5-day fasts alternating with 3-day intervals on 500 KCal/day with 60 g protein, in a group of 21 obese women a significant decline of the hexokinase activity in skeletal muscle was found. Other enzymes: triosophosphate dehydrogenase, lactate dehydrogenase, glycerol-3-phosphate dehydrogenase, citrate synthase, malate dehydrogenase and hydroxyacyl-CoA dehydrogenase showed no significant changes. There was a significant fall in concentration of DNA and and glycogen, but the protein concentration did not change.
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PMID:Effect of protracted intermittent fasting on the activities of enzymes involved in energy metabolism, and on the concentrations of glycogen, protein and DNA in skeletal muscle of obese women. 102 20


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