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)

An immobilized three-enzyme system, malate dehydrogenase (EC 1.1.1.37)-citrate synthase (EC 4.1.3.7)-lactate dehydrogenase (EC 1.1.1.27), was investigated as a model for the rate of oxalacetate production and utilization in mitochondria. Lactate dehydrogenase is included to mimic the NADH-utilizing system of mitochondria. This three-enzyme system was immobilized in three different ways (1) on Sephadex G-50 (surface coupling), (2) on Sepharose 4B (internal-external coupling), and (3) entrapped in polycrylamide gel. The rate of citrate production from malate, NAD(+), and acetyl CoA was determined continuously in a flow system. Up to about 100% rate enhancements were observed when the immobilized system was compared to identical systems of free enzyme. An even more pronounced increase of rate of up to about 400% compared to the soluble system was measured after addition of pyruvate (to reoxidize formed NADH). These results are interpreted in relation to microenvironmental changes of oxalacetate production and the possible organization of enzymes of the Krebs cycle.
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PMID:An immobilized three-enzyme system: a model for microenvironmental compartmentation in mitochondria. 435 55

During exponential growth, ordinary colorless (OC) plants of Blastocladiella emersonii consumed little glucose and produced no lactic acid. Similarly, resistant sporangial (RS) plants did not utilize glucose or produce lactic acid during the first 24 hr of exponential growth. During the next 24 hr of RS development, glucose was consumed with the concomitant production of lactic acid which was then reutilized. Lactic acid gradually accumulated again at maturity. Enzyme studies on cell-free extracts indicated the presence of all tricarboxylic cycle enzymes except alpha-ketoglutarate dehydrogenase at all stages of development of both RS and OC plants. Included among the enzymes detected were an adenosine monophosphate-stimulated, nicotinamide adenine dinucleotide-isocitric dehydrogenase, and citrate-condensing enzyme. When measured on a per plant basis, tricarboxylic cycle enzyme levels increased during the exponential growth of both kinds of plants. Only after the bicarbonate ceased to have effect on RS plant morphogenesis was there a decrease in the levels of the tricarboxylic cycle enzymes when measured on a per plant basis. Specific activity measurements indicated some differences in the differential rates of synthesis among the enzymes studied previous to 36 hr. Preliminary studies utilizing short periods of (14)C-bicarbonate fixation in young RS plants indicated that during the first 4 min most of the label was located in aspartic acid. These results are discussed in terms of previous results and particularly Cantino's hypothesis concerning the relationship between bicarbonate induction and tricarboxylic-cycle enzymes in the morphogenesis of B. emersonii.
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PMID:Tricarboxylic acid cycle enzymes and morphogenesis in Blastocladiella emersonii. 580 5

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

Single canine Purkinje cells were isolated by microdissection and analyzed quantitatively for six enzymes of energy metabolism. Subendocardial Purkinje cells were clearly distinguishable morphologically and biochemically from adjacent myocardium and had enzyme levels comparable with extramural Purkinje cells. Oxidative enzymes, citrate synthase, malate dehydrogenase, and beta-hydroxyacyl CoA dehydrogenase were 40-60% lower in Purkinje cells than in myocardium. Lactate dehydrogenase was also 40% lower, but the other glycolytic enzymes, hexokinase and phosphofructokinase, were similar in level in myocardium and Purkinje cells. The results of this study show that it is completely practicable to apply quantitative histochemical analysis to biochemical study of the cardiac conducting system.
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PMID:Quantitative histochemistry of canine cardiac Purkinje fibers. 622 55

Enzyme activities were determined in pools of type I (slow twitch) and II A and II B (fast twitch) fibres of the thigh muscle from individuals engaged to a high degree in physical training of an endurance character and from non-endurance-trained controls. The endurance-trained (ET) group had significantly higher activity levels of the mitochondrial enzymes citrate synthase, malate dehydrogenase, and 3-OH-acylCoA dehydrogenase both in type I (2.1X, 1.7X, 1.4X) and in type II A (2.3X, 1.8X, 1.4X) and II B fibres (2.0X, 1.5X, 1.5X) than the non-endurance-trained (NET) group. Of the glycolytic enzymes, phosphofructokinase (PFK) in type I fibres was significantly higher (1.8X) in the ET than in the NET group whereas glyceraldehydephosphate dehydrogenase (GAPDH) in type I fibres was similar in the two groups. In type II fibres both PFK and GAPDH levels tended to be higher in the ET group. Lactate dehydrogenase (LDH) of both fibre types were not different in the two groups. Type I fibres differed significantly from type II fibres for all the six enzymes measured in both groups. However, no significant difference between fibres of types II A and II B was found. The results indicate that fibres of types I, II A and II B in human skeletal muscle all possess great adaptability with regard to their oxidative capacity. Furthermore, the data suggest that extensive endurance training may enhance the glycolytic capacity in both type I and type II fibres although the glycolytic capacity of the muscle as a whole generally is low in endurance trained subjects owing to a predominance of type I fibres. It is concluded that further studies are needed to determine whether there is a metabolic distinction between fibres of types II A and II B.
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PMID:Enzyme levels in pools of microdissected human muscle fibres of identified type. Adaptive response to exercise. 623 50

The metabolic recovery potential of muscle was studied in regenerating soleus muscles of young adult rats. Degeneration was induced by subfascial injection of a myotoxic snake venom. After regeneration for selected periods up to 2 weeks, samples of whole muscle were analysed for hexokinase (EC 2.7.1.1), phosphofructokinase (EC 2.7.1.11), lactate dehydrogenase (EC 1.1.11.27), adenylokinase (EC 2.7.4.3), creatine kinase (EC 2.7.3.2), malate dehydrogenase (EC 1.1.11.37), citrate synthase (EC 4.1.3.7) and beta-hydroxyacyl CoA dehydrogenase (EC 1.1.1.35). Lactate dehydrogenase, adenylokinase, malate dehydrogenase and beta-hydroxyacyl CoA dehydrogenase were also measured in individual fibres of muscle regenerating up to 4 weeks. We found that in the presence of nerve there was complete recovery of muscle metabolic capacity. However, there were differences in the rate of recovery of the activity of enzymes belonging to different energy-generating pathways. Lactate dehydrogenase, an enzyme representing glycolytic metabolism, reached normal activity immediately upon myofibre formation, only 3 days after venom injection, while oxidative enzymes required a week or more to reach normal activity levels. The delay in oxidative enzyme recovery coincided with physiological parameters of reinnervation. Therefore, to further test the role of nerve on the metabolic recovery process, muscle regeneration was studied following venom-induced degeneration coupled with denervation. In the absence of innervation, most enzymes failed to recover to normal activity levels. Lactate dehydrogenase was the only enzyme to achieve normal levels, and it did so as rapidly as in innervated-regenerating soleus muscles. The remainder of the glycolytic enzymes and the high energy phosphate enzymes recovered only partially. Oxidative enzymes showed no recovery and were severely reduced in the absence of reinnervation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nerve-dependent recovery of metabolic pathways in regenerating soleus muscles. 786 Jul 5

The metabolism of [1-13C]glucose in rat cerebellum astrocytes and granule cells was investigated using 13C- and 1H-NMR spectroscopy. Near homogeneous primary cultures of each cell type were incubated with [1-13C]glucose, under the same conditions. Analysing the relative 13C enrichments of metabolites in spectra of cell perchloric acid extracts, on the one hand, the 13C-1H spin-coupling patterns in 1H-NMR spectra of cell medium lactate and the 13C-13C spin-coupling patterns in 13C-NMR spectra of purified cell glutamate, on the other hand, showed significant differences, between the two cell types, in the activity of various metabolic ways. First, the carbon flux through the oxidative branch of the hexose monophosphate shunt, which leads to unenriched lactate, was found higher in granule cells than in astrocytes. Second, although the specific 13C enrichment of lactate was higher in astrocytes than in granule cells, the fraction of 13C-enriched acetyl-CoA entering the citric acid cycle was more than twice as high in granule cells as in astrocytes. Lactate C3 and acetyl-CoA C2 enrichments were very similar in granule cells, whereas acetyl-CoA C2 enrichment was 60% lower than that of lactate C3 in astrocytes. These results can be explained by the fact that granule cells used almost exclusively the exogenous glucose to fuel the citric acid cycle, whereas astrocytes used concomitantly glucose and other carbon sources. Last, in the case of granule cells, glutamate C2 and C3 enrichments were equivalent; the carbon flux through the pyruvate carboxylase route was evaluated to be around 15% of the carbon flux through the citrate synthetase route. In astrocytes, glutamate C2 enrichment was higher than that of C3, which could be explained by a pyruvate carboxylase activity much more active in these cells than in granule cells.
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PMID:[1-13C]glucose metabolism in rat cerebellar granule cells and astrocytes in primary culture. Evaluation of flux parameters by 13C- and 1H-NMR spectroscopy. 790 Oct 11

Energy metabolism and the substrate utilization pattern of intact porcine carotid artery were investigated in the presence or absence of glucose and/or octanoate during the phases of isometric contraction induced by K+ depolarization. During the early phase of contraction, there was a rapid increase in the rate of O2 uptake that was independent of the rate of force generation but dependent on the availability of intracellular pyruvate, the source of which was glucose and not glycogen. Lactate production increased linearly from the onset of contractile stimulation and was not suppressed by octanoate oxidation. There was no alteration from the basal resting state in the concentrations of the metabolites of the tricarboxylic acid cycle in the presence or absence of octanoate. During the phase of steady-state force maintenance, O2 consumption was increased compared with the basal unstimulated rate but was not increased when glucose and octanoate were present, which is consistent with the Crabtree effect. This was associated with increased aerobic lactic acid production and inhibition of the tricarboxylic acid cycle at the citrate synthase step. Alteration of the high-energy phosphate content could not account for the pattern of O2 consumption during contraction under different substrate conditions. In the absence of glucose, the energy from octanoate oxidation could substitute for the energy ordinarily derived from aerobic glycogen and lactic acid production. It is concluded that energy metabolism of vascular smooth muscle is coordinated during contraction by integration of the pathways of aerobic glycolysis and oxidative phosphorylation.
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PMID:Substrate-dependent alteration in O2 consumption and energy metabolism in vascular smooth muscle. 876 34

Although endurance training enhances the antioxidant defence of different tissues, information on the effect of sprint training is scanty. We examined the effect of sprint training on rat skeletal muscle and heart antioxidant defences. Male Wistar rats, 16-17 weeks old, were sprint trained on a treadmill for 6 weeks. Total glutathione levels and activities of glutathione peroxidase, glutathione reductase, glutathione S-transferase and superoxide dismutase in heart and various skeletal muscles were compared in trained and control sedentary animals. Lactate dehydrogenase and citrate synthase enzyme activities were measured in muscle to test the effects of training on glycolytic and oxidative metabolism. Sprint training significantly increased lactate dehydrogenase activity in predominantly fast glycolytic muscles and enhanced total glutathione contents of the superficial white quadriceps femoris, mixed gastrocnemius and fast-glycolytic extensor digitorum longus muscles. Oxidative metabolic capacity increased in plantaris muscle only. Compared with the control group, glutathione peroxidase activities in gastrocnemius, extensor digitorum longus muscles and heart also increased in sprint trained rats. Glutathione reductase activities increased significantly in the extensor digitorum longus muscle and heart. Glutathione S-transferase activity was also higher in the sprint trained extensor digitorum longus muscle. Sprint training did not influence glutathione levels or glutathione-related enzymes in the soleus muscle. Superoxide dismutase activity remained unchanged in skeletal muscle and heart. Sprint training selectively enhanced tissue antioxidant defences by increasing skeletal muscle glutathione content and upregulating glutathione redox cycle enzyme activities in fast and mixed fibre leg muscles and heart.
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PMID:Skeletal muscle and heart antioxidant defences in response to sprint training. 889 59

We investigated the effects of 4 wk of hypodynamia on the rate of lactate transport in skeletal muscle sarcolemmal vesicles from control and hindlimb-suspended rats. Characterization of the sarcolemmal preparations was achieved with a marker enzyme (K+-p-nitrophenylphosphatase) and measurement of 1 mM [U-14C]lactate transport activity under zero-trans conditions with or without a pH gradient or the transport inhibitor alpha-hydroxycinnamate. Preparations from the two groups were not significantly different concerning yield and purification. Based on these results, we used this model to analyze the lactate transport activity after hypodynamia by tail suspension. Hindlimb suspension caused a shift from slow to fast myosin heavy chain isoforms in soleus muscles with a 40% decrease in the citrate synthase activity (from 35.3 +/- 3.7 to 21.4 +/- 2.1 mu mol x g-1 x min-1; P < 0.05). Lactate (1 mM) uptake in vesicles from the two groups was a function of time, and the rate after hindlimb suspension was significantly decreased in the suspended compared with the control group (2.25 +/- 0.44 and 3.50 +/- 0.26 nmol x min-1 x mg protein-1, respectively; P < 0.05). These differences were not observed for a higher lactate concentration (50 mM). These results suggest that the level of physical activity plays a role in the regulation of sarcolemmal lactate transport activity implicated in the exchanges of lactate between producing and utilizing cells, organs, and tissues, which are major ways of carbohydrate energy distribution in humans and others species.
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PMID:Lactate uptake by skeletal muscle sarcolemmal vesicles decreases after 4 wk of hindlimb unweighting in rats. 892 78


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