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)

The effects of intermittent infusions of dobutamine were studied in young normal male subjects during a period of bedrest deconditioning to determine whether this synthetic catechol affects physical conditioning processes in humans. 24 volunteers were placed at bedrest and randomized to daily 2-h treatments of saline infusions (control), dobutamine infusions, or maintenance exercise (control). Exercise, hemodynamic, and metabolic studies were performed at base line and at the termination of the 3-wk treatment period. Maximal exercise (duration, oxygen consumption, and workload) fell for the saline group and remained unchanged for the dobutamine and exercise groups. Hemodynamics during exercise were maintained the same as pretreatment base line for the dobutamine and exercise groups, whereas stroke volume and cardiac output dropped and heart rate rose for the saline group. The metabolic profile showed an increased blood lactate response at rest and during submaximal exercise after 3 wk of bedrest for the saline group, and essentially no change for the exercise and the dobutamine groups. Extraction of oxygen across the exercising lower limb rose for the dobutamine group, as did the activity of the skeletal muscle oxidative enzymes, citrate synthetase, and succinate dehydrogenase. In contrast to the exercise control group, the saline and dobutamine groups developed orthostatic hypotension, tachycardia, and accentuation of the renin-aldosterone response over the 3-wk treatment period; for the saline group, this is best explained by the observed fall in blood volume and for the dobutamine group, by the blunting of vascular vasoconstrictive responses. During a period of bedrest deconditioning in humans, infusions of dobutamine maintain many of the physiologic expressions of physical conditioning.
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PMID:Prevention of bedrest-induced physical deconditioning by daily dobutamine infusions. Implications for drug-induced physical conditioning. 393 70

Some enzyme activities and metabolic features of the black Ma melanotic, brown MI melanotic and Ab amelanotic melanomas of hamster were investigated. The activities of hexokinase and phosphofructokinase were similar in all three melanomas, the activity of NAD-dependent glycerol-3-phosphate dehydrogenase was higher in the amelanotic melanoma and that of pyruvate kinase and lactate dehydrogenase were slightly lower in MI than in the other tumors. The activities of citrate synthase, succinate dehydrogenase and malate dehydrogenase were higher in the Ma and MI melanotic melanomas than in the Ab amelanotic melanoma. The rate of labeled CO2 production from 6-14C-glucose, 1,5-14C-citric acid and U-14C-glutamine was about 2 times higher in melanotic melanomas than in amelanotic one, while no significant differences among the three melanomas were found in respect to 1-14C-glucose and U-14C-glycerol-3-phosphate. The production of 14CO2 was much higher from 1-14C-glucose than from 6-14C-glucose in all the melanomas studied. L-DOPA stimulated the production of 14CO2 from 1-14C-glucose much stronger in the Ma and MI melanomas than in the Ab melanoma. In none of the tumors the incorporation from 6-14C-glucose to CO2 was affected by L-DOPA. It is postulated that oxidation of glucose via the pentose phosphate cycle is involved in melanogenesis.
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PMID:Metabolic characterization of three hamster melanoma variants. 406 92

Crude extracts of both vegetative cells and glycerol-induced microcysts of Myxococcus xanthus contained the following enzyme activities: phosphofructokinase, phosphoglucoisomerase, fructose-1,6-diphosphatase, fructosediphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase, phosphopyruvate carboxylase, citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucomutase, and uridine diphosphate glucose pyrophosphorylase. With the exception of isocitrate dehydrogenase, which was present at a fivefold higher concentration in microcysts, all activities in extracts from both types of cells were essentially equal. Hexokinase and pyruvate kinase could not be detected in extracts from either type of cell. Microcysts metabolized acetate at a lower rate than did vegetative cells. Most of this decrease was reflected in a substantial decrease in ability of microcysts to oxidize acetate to CO(2). In addition, microcysts and vegetative cells showed a different distribution of (14)C-label from incorporated acetate.
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PMID:Comparative intermediary metabolism of vegetative cells and microcysts of Myxococcus xanthus. 430 96

A technique was developed for the detection, on agar, of mutants of Bacillus subtilis that lacked a functional tricarboxylic acid cycle. Mutants devoid of detectable levels of aconitase, isocitric dehydrogenase, alpha-ketoglutarate dehydrogenase, succinic dehydrogenase, fumarase, and malate dehydrogenase have been isolated and characterized. Several mutants with conditionally expressible lesions, including a mutant with a heat-sensitive citrate synthase, have also been isolated. All of the mutants examined express all the biochemical markers normally absent in early-stage sporulation mutants except elastase, and some of these mutants sporulated nearly as well as the prototroph.
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PMID:Isolation and characterization of tricarboxylic acid cycle mutants of Bacillus subtilis. 499 41

The growth response of Listeria monocytogenes strains A4413 and 9037-7 to carbohydrates was determined in a defined medium. Neither pyruvate, acetate, citrate, isocitrate, alpha-ketoglutarate, succinate, fumarate, nor malate supported growth. Furthermore, inclusion of any of these carbohydrates in the growth medium with glucose did not increase the growth of Listeria over that observed on glucose alone. Resting cell suspensions of strain A4413 oxidized pyruvate but not acetate, citrate, isocitrate, alpha-ketoglutarate, succinate, fumarate, or malate. Cell-free extracts of strain A4413 contained active citrate synthase, aconitate hydratase, isocitrate dehydrogenase, malate dehydrogenase, fumarate hydratase, fumarate reductase, pyruvate dehydrogenase system, and oxidases for reduced nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate. The alpha-ketoglutarate oxidation system, succinate dehydrogenase, isocitrate lyase, and malate synthase were not detected. Cytochromes were not detected. The data suggest that strain A4413, under these conditions, utilizes a split noncyclic citrate pathway which has an oxidative portion (citrate synthase, aconitate hydratase, and isocitrate dehydrogenase) and a reductive portion (malate dehydrogenase, fumarate hydratase, and fumarate reductase). This pathway is probably important in biosynthesis but not for a net gain in energy.
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PMID:Citrate cycle and related metabolism of Listeria monocytogenes. 499 14

The activities of the eight citric acid-cycle enzymes of rat bone-marrow cells were determined along with several other mitochondrial and non-mitochondrial enzymes. Four of the citric acid-cycle enzymes (aconitase, succinyl-CoA thiokinase, alpha-oxoglutarate dehydrogenase and succinate dehydrogenase) have closely similar low activities; two [isocitrate dehydrogenase (NAD) and citrate synthase] have intermediate activities; the remaining two (malate dehydrogenase and fumarase) have high activities. The other enzymes surveyed also exhibited a spread of three orders of magnitude, the mitochondrial enzymes showing no less variation than the others.
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PMID:The activities of the citric acid-cycle enzymes in rat bone-marrow cells. 566 55

Sixteen male subjects (20-31 yr) trained for 8 wk on cycle ergometers. Eight of the subjects were treated during the training period with the beta-adrenoceptor blocker propranolol (160 mg/day). During all pre-and posttraining tests, subjects were uninfluenced by the medication. Training-induced increases in VO2max and decreases in blood lactate and norepinephrine concentrations at submaximal exercise were not different between the beta-blockade and the placebo groups. The activities of the mitochondrial enzymes citrate synthase (CS), succinate dehydrogenase (SDH), cytochrome c oxidase (Cyt-c-ox), and 3-hydroxyacyl-CoA dehydrogenase (HAD) in the quadriceps femoris muscle increased significantly (P less than 0.01) with training (beta-blockade group, +47, +33, +38, and 22%; placebo group, +75, 70, +87, and +63%, respectively). Cyt-c-ox and HAD increased significantly more in the placebo group than in the beta-blockade group, while a tendency to an increase was noted for SDH. Muscle capillary density increased similarly (+17-19%) with training in the two groups (P less than 0.01). In conclusion, subjects training under the influence of a therapeutic level of beta-adrenergic blockade show marked increases in both the respiratory capacity and the capillary supply of the engaged skeletal muscles. However, the increase in muscle mitochondrial enzymes may be less apparent than in the normal state.
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PMID:Beta-adrenergic blockade and training in human subjects: effects on muscle metabolic capacity. 608 81

The contribution of muscle tissue to the increased metabolic efficiency of the obese (fa/fa) Zucker rat at 6 wk of age was examined. In vitro O2 consumption was similar in obese and nonobese soleus and extensor digitorum longus (EDL) muscles, whether the animals were fed ad libitum, fasted, or treated with triiodothyronine. No phenotypic difference in the in vitro O2 consumption was seen when the muscles were preincubated with or without exogenous insulin. Pyruvate kinase, citrate synthase, succinate dehydrogenase, and cytochrome oxidase activities were similar in the soleus and the EDL muscles of both phenotypes. Phosphofructokinase and lactate dehydrogenase activities were higher in the soleus muscles from the obese rats, whereas hexokinase activities were higher in the EDL muscles from the nonobese rats. Mitochondrial and whole muscle homogenate respiration rates were similar in both phenotypes. The soleus and EDL muscles from the obese animals weighed less than those from the nonobese, but empty carcass weights were similar. Taken together these data suggest that muscle mass, muscle O2 consumption, and muscle oxidative capacity are similar in 6-wk-old obese and nonobese rats. Therefore other tissues are probably responsible for the increased metabolic efficiency of the young obese rat.
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PMID:Oxygen consumption and oxidative capacity of muscles from young obese and nonobese Zucker rats. 609 7

Rats were trained by daily running exercises for 7 weeks. In addition, one group of rats was trained under the influence of propranolol, while another group received daily injections of propranolol only. None of the treatments used had influence on the activities of myocardial enzymes: 3-hydroxyacyl-CoA - dehydrogenase (HADH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), and citrate synthase (CS) which were assayed for estimating oxidative capacity, or lactate dehydrogenase (LDH) which was used as a measure of anaerobic capacity. Training without propranolol resulted in elevated activities of the oxidative enzymes in M. extensor digitorum and in M. soleus. The corresponding changes in the rat group trained with propranolol always were much smaller, despite an equal amount of training. Only the trend for lowered activity of LDH was observable in skeletal muscle of the rat groups trained both with and without propranolol. Long-term beta-blockade alone did not induce enzymatic changes. It is concluded that a functioning sympathetic nervous system is necessary for the adaptive responses of muscular metabolism to training. Blockade of the sympathetic influence during exercise periods also hampers the training-induced responses.
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PMID:Physical training under the influence of beta-blockade in rats. III. Effects on muscular metabolism. 610 47

Cells of the aerotolerant anaerobe Giardia lamblia respire in the presence of oxygen. Endogenous respiration is stimulated by glucose but not by other carbohydrates and Krebs cycle intermediates. Endogenous and glucose-stimulated respiration are insensitive to cyanide, malonate, and 2,4-dinitrophenol, but are inhibited by atabrin and iodoacetamide. G. lamblia produces ethanol, acetate and CO2 both aerobically and anaerobically either from endogenous reserves or exogenous glucose. Molecular hydrogen is not produced. The following enzyme activities were detected in homogenates: hexokinase, fructose-biphosphate aldolase, pyruvate kinase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, malate dehydrogenase (decarboxylating), pyruvate synthase, acetyl-CoA synthetase, alcohol dehydrogenase (NADP+), NADH dehydrogenase, NADPH dehydrogenase, NADPH oxidoreductase and superoxide dismutase. The enzymes of energy and carbohydrate metabolism are nonsedimentable (109 000 x g for 30 min). Activities of lactate dehydrogenase, hydrogenase, phosphate acetyltransferase, acetate kinase, citrate synthase, succinate dehydrogenase, fumarate hydratase and catalase were below the limits of detection. The results suggest the occurrence of glycolysis, energy production by substrate level phosphorylation and a flavin, iron-sulfur protein mediated electron transport system as well as the absence of cytochrome mediated oxidative phosphorylation and functional Krebs cycle.
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PMID:Energy metabolism of the anaerobic protozoon Giardia lamblia. 610 7


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