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)

It has been reported that the mitochondrial cytochromes and citrate cycle enzymes occur in constant proportions to each other and increase or decrease roughly in parallel in response to various stimuli. The purpose of this study was to determine whether this proportionality is an obligatory consequence of the way in which mitochondria are assembled. Severe iron deficiency was used to bring about decreases of the iron-containing constituents of the mitochondrial respiratory chain in skeletal muscle. Cytochrome c concentration and cytochrome oxidase activity were decreased approximately 50%, while succinate dehydrogenase and NADH dehydrogenase activities were decreased by 78% in iron-deficient muscle. On electron microscopic examination, mitochondria in iron-deficient muscles had relatively sparse numbers of cristae. The iron deficiency had little or no effect on the levels of a range of mitochondrial matrix enzymes, including citrate synthase, isocitrate dehydrogenase, fumarase, aspartate aminotransferase, 3-hydroxyacyl-CoA dehydrogenase, 3-ketoacid-CoA transferase, and acetoacetyl-CoA thiolase. These results show that the usual constant proportions between the constituents of the mitochondrial respiratory chain and matrix enzymes are not obligatory; they provide evidence that mitochondrial matrix enzymes and respiratory chain constituents can be incorporated into mitochondria independently and that the ratios between them can vary within wide limits.
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PMID:Perturbation of mitochondrial composition in muscle by iron deficiency. Implications regarding regulation of mitochondrial assembly. 302 53

The contribution of the liver to the increased metabolic efficiency of the obese rat (fa/fa) was examined. Oxygen consumption of isolated hepatocytes and isolated mitochondria, and hepatic activities of mitochondrial enzymes were measured. Hepatocyte oxygen consumption was similar in the obese and nonobese rats for all substrates tested. Mitochondrial respiration also was similar in both phenotypes for all substrates tested. Activities of citrate synthase, succinate dehydrogenase, and cytochrome oxidase were similar for obese and nonobese rats. Taken together, these data show that in vitro hepatic oxygen consumption and oxidative capacity are similar in obese and nonobese rats. Rates of mitochondrial respiration with palmitoylcarnitine further show that the capacity for hepatic lipid oxidation is similar in obese and nonobese rats. Therefore, the increased metabolic efficiency of the obese rat probably cannot be attributed to an intrinsic decreased hepatic oxidative capacity. Further, there is no defect in hepatic lipid oxidative capacity in the young obese rat.
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PMID:Oxygen consumption and oxidative capacity of hepatocytes from young male obese and nonobese Zucker rats. 302 May 65

The sensory projections from the whiskers of mice and other rodents synapse somatotopically in 3 subnuclei in the brainstem trigeminal complex, in the ventrobasal complex of the thalamus and in the somatosensory cortex. Deafferentation of the whiskers in adult animals results in qualitative and quantitative changes in activities of the metabolic enzymes in the somatosensory cortex (e.g. J. Neuro-sci., 1 (1981) 929-935). We determined the time course and extent of changes in the subcortical trigeminal centers of adult mice after deafferentation. The right infraorbital nerve was sectioned in mice under surgical anesthesia; the animals survived for periods up to 26 weeks. The optic nerve was also cut to evaluate the effects of central tract section. Some brains were prepared histochemically for the mitochondrial enzymes cytochrome oxidase (CO) and succinic dehydrogenase (SDH), and some were prepared for microchemical analysis of the enzymes citrate synthase (CS), malate dehydrogenase (MDH) and phosphorylase. All deafferented and intact nuclei were examined in each animal quantitatively. The oxidative enzymes (CO, SDH, CS and MDH) that were analyzed by histochemical and microchemical approaches showed a decrease in activities as early as 3 weeks postdeafferentation, a trend that continued up to 12 weeks in all the subcortical trigeminal stations and lateral geniculate nucleus (LGN) when compared with the intact side. By 25 weeks postlesion, the levels were comparable to the intact side except that in the LGN, the levels remained depressed. The phosphorylase levels increased at around 3 weeks postoperation and remained elevated 25 weeks postlesion. Each case provided results on the effects of deafferentation at a given time point throughout the trigeminal pathway. Direct quantitative correlation of histochemical and microchemical approaches for glycolytic enzymes is consistent with a coordinate regulation of these molecules. The changes in enzyme levels in all nuclei occur simultaneously and to a similar degree. This strongly suggests that neuronal activity plays an important role in regulating metabolic machinery throughout this pathway in adults.
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PMID:Quantitative histochemical and microchemical changes in the adult mouse central nervous system after section of the infraorbital and optic nerves. 303 55

In the present study the effects of chronic administration of dextroamphetamine on energy metabolism in the brain of the rat were examined. The enzymes studied were: hexokinase (soluble and particulate forms), phosphofructokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase, NAD+ and NADP+-dependent isocitrate dehydrogenases, succinate dehydrogenase and malate dehydrogenase. All the activities of the enzymes were assayed in four regions of the brain of the rat (cerebellum, medulla oblongata and pons, cererbral cortex and diencephalon). Rats were injected intaperitoneally once daily with dextroamphetamine for 20 consecutive days. The initial dose was 5 mg/kg/day and the dose was then increased by 1 mg/kg/every 5 days up to a total of 8 mg/kg/day on days 16-20. In the glycolytic enzymes a reduction of the activity of phosphofructokinase was found in the diencephalon and an increase of the activity of pyruvate kinase and lactate dehydrogenase in the diencephalon and medulla oblongata and pons, respectively. Citrate synthase was the only enzyme in the Krebs' cycle affected by chronic administration of dextroamphetamine. The results presented here show that chronic administration of dextroamphetamine produced important changes in some enzymes of glycolysis and the Krebs' cycle in the brain of the rat.
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PMID:Effects of chronic administration of dextroamphetamine on enzymes of energy metabolism in regions of the rat brain. 303 25

The activities of the mitochondrial enzymes citrate synthase (citrate oxaloacetatelyase, EC 4.1.3.7), NADP-linked isocitrate dehydrogenase (threo-Ds-isocitrate:NADP+ oxidoreductase (decarboxylating), EC 1.1.1.42), and succinate dehydrogenase (succinate: FAD oxidoreductase, EC 1.3.99.1) as well as their kinetic behavior in the two developmental forms of Trypanosoma cruzi at insect vector stage, epimastigotes and infective metacyclic trypomastigotes, were studied. The results presented in this work clearly demonstrate a higher mitochondrial metabolism in the metacyclic forms as is shown by the extraordinary enhanced activities of metacyclic citrate synthase, isocitrate dehydrogenase, and succinate dehydrogenase. In epimastigotes, the specific activities of citrate synthase at variable concentrations of oxalacetate and acetyl-CoA were 24.6 and 26.6 mU/mg of protein, respectively, and the Michaelis constants were 7.88 and 6.84 microM for both substrates. The metacyclic enzyme exhibited the following kinetic parameters: a specific activity of 228.4 mU/mg and Km of 3.18 microM for oxalacetate and 248.5 mU/mg and 2.75 microM, respectively, for acetyl-CoA. NADP-linked isocitrate dehydrogenase specific activities for epimastigotes and metacyclics were 110.2 and 210.3 mU/mg, whereas the apparent Km's were 47.9 and 12.5 microM, respectively. No activity for the NAD-dependent isozyme was found in any form of T. cruzi differentiation. The particulated succinate dehydrogenase showed specific activities of 8.2 and 39.1 mU/mg for epimastigotes and metacyclic trypomastigotes, respectively, although no significant changes in the Km (0.46 and 0.48 mM) were found. The cellular role and the molecular mechanism that probably take place during this significant shift in the mitochondrial metabolism during the T. cruzi differentiation have been discussed.
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PMID:Differential energetic metabolism during Trypanosoma cruzi differentiation. I. Citrate synthase, NADP-isocitrate dehydrogenase, and succinate dehydrogenase. 305 38

A transcript analysis of the citrate synthase and succinate dehydrogenase genes (gltA-sdhCDAB) of Escherichia coli was done by nuclease S1 mapping. Evidence was obtained for two monocistronic gltA transcripts extending anti-clockwise, to a common terminus, from independent promoters with start points 196 bp (major) and 299 bp (minor) upstream of the gltA coding region. Evidence was also obtained for two polycistronic sdh transcripts, sdhCDAB (minor) and sdhDAB (major), extending clockwise, from sites 219 bp upstream of sdhC and 1455 bp upstream of sdhD (i.e. within sdhC), to a common terminus. The synthesis of all of the transcripts was repressed by growth in the presence of glucose, and this is consistent with the well-established fact that both enzymes are subject to catabolite repression. Sequences resembling known binding sites for the cAMP-CRP (cyclic AMP-cyclicAMP receptor protein) complex occur in the vicinity of each promoter suggesting that they are activated by the cAMP-CRP complex.
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PMID:Transcript analysis of the citrate synthase and succinate dehydrogenase genes of Escherichia coli K12. 330 32

We studied energy metabolism after experimental subarachnoid hemorrhage in rats. Four different cerebral areas were tested: frontal cortex, occipital cortex, hippocampus, and brainstem. Vmax of the following enzymatic activities was evaluated: in the homogenate: hexokinase, phosphofructokinase, and lactate dehydrogenase for the glycolytic pathway, and glucose-6-phosphate dehydrogenase for the hexose monophosphate shunt; in the purified nonsynaptic mitochondria: NAD+-isocitrate dehydrogenase, citrate synthase, and succinate dehydrogenase for the Krebs cycle, and cytochrome oxidase for the electron transfer chain. We also evaluated some parameters related to the respiration of nonsynaptic mitochondria (State 3, State 4, uncoupled state, respiratory control ratio, and ADP:O ratio). Subarachnoid hemorrhage did not significantly affect Vmax of the enzymatic activities related to anaerobic and aerobic metabolism; however, mitochondrial respiration was affected, particularly in the presence of NADH-producing substrates (glutamate + malate).
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PMID:Bioenergetics of different brain areas after experimental subarachnoid hemorrhage in rats. 335 25

Aerobic and anaerobic thresholds determined by different methods in repeated exercise tests were correlated with cardiorespiratory variables and variables of muscle metabolic profile in 33 men aged 20-50 years. Aerobic threshold was determined from blood lactate, ventilation, and respiratory gas exchange by two methods (AerT1 and AerT2) and anaerobic threshold from venous lactate (AnTLa), from ventilation and gas exchange (AnTr) and by using the criterion of 4 mmol.1(-1) of venous lactate (AnT4mmol). In addition to ordinary correlative analyses, applications of LISREL models were used. The 8 explanatory variables chosen for the regression analyses were height, relative heart volume, relative diffusing capacity of the lung, muscle fiber composition, citrate synthase (CS) and succinate dehydrogenase activities, the lactate dehydrogenase--CS ratio, and age. They explained 58% of the variation in AerT1, 73.5% that of AerT2, 71% that of AnTr, 74.5% that of AnTLa, and 67.5% that of AnT4mmol.AerT and AnT alone explained 77% of the variation in each other. Both AerT and AnT were determined mainly by a muscle metabolic profile, with the CS activity of vastus lateralis as the strongest determinant. The factor 'submaximal endurance' which was measured with AerT and AnT seemed to be slightly more closely connected to 'muscle metabolic profile' than was 'maximal aerobic power' (= VO2max), but both also correlated strongly with each other (r = 0.92).
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PMID:Muscle metabolic profile and oxygen transport capacity as determinants of aerobic and anaerobic thresholds. 341 58

The genes encoding both subunits of the succinyl-CoA synthetase of Escherichia coli have been identified as distal genes of the suc operon, which also encodes the dehydrogenase (Elo; sucA) and succinyltransferase (E2o; sucB) components of the 2-oxoglutarate dehydrogenase complex. The newly defined genes express polypeptides of 41 kDa (sucC) and 31 kDa (sucD), corresponding to the beta and alpha subunits of succinyl-CoA synthetase, respectively. The genes are thus located at 16.8 min in the E. coli linkage map, together with the citrate synthase (gltA) and succinate dehydrogenase (sdh) genes, in a cluster of nine citric acid cycle genes: gltA-sdhCDAB-sucABCD. Four deletion strains lacking all of these citric acid cycle enzymes were characterized. The succinyl-CoA synthetase activities of strains harbouring plasmids containing the sucC and sucD genes were amplified some fourfold. Further enzymological studies indicated that expression of succinyl-CoA synthetase is coordinately regulated with 2-oxoglutarate dehydrogenase.
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PMID:Cloning and expression of the succinyl-CoA synthetase genes of Escherichia coli K12. 354 12

The effect of severe protein deprivation and subsequent nutritional rehabilitation on the fibre size and mitochondrial enzyme activity of the extensor digitorum longus (EDL) and soleus muscles of the young rat has been examined. Protein deprived rats showed atrophy of type 2 fibres predominantly, reduced histochemical activity of succinic dehydrogenase (SDH) and reduced biochemical activity of citrate synthase. Nutritional rehabilitation indicated by resumption of the original body weight resulted in complete restitution of the weight of the muscles and the size of type 1 and type 2 fibres, but not of the activity of SDH and citrate synthase. The results indicate that regarding size, type 2 fibres tend to be more influenced than type 1 fibres by the nutritional supply. The mitochondrial enzyme activity which is decreased by protein deprivation does not regain the normal levels as quickly as the muscle fibres resume their normal size.
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PMID:Nutritional rehabilitation of skeletal muscle in protein-deprived young rats. 376 Sep 9


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