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)

Sarcoplasmic reticulum vesicles and mitochondria were prepared from red and white skeletal muscles of the rabbit. The preparations were characterized in terms of their specific activities of citrate synthase, basal (Mg2+-dependent) and Ca2+-dependent ATPase (the latter two in the presence of NaN3 and ouabain), and their specific carbonic anhydrase activities were determined. Skeletal muscle mitochondria had high specific activities of citrate synthase (700-1200 mu. mg protein-1) and low carbonic anhydrase activities (0.1-0.4 u. ml mg protein-1). The latter are likely to be due to a contamination of the preparations with sarcoplasmic reticulum (s.r.) Preparations of s.r. vesicles showed negligible activities of citrate synthase and the expected differing patterns of basal and Ca2+-dependent ATPase in red and white muscles. Specific carbonic anhydrase activities in s.r. from both muscle types were high (2-4 u. ml mg protein-1). The highest carbonic anhydrase activity, 11 u. ml mg protein-1, was found in s.r. from rabbit m. masseter. The inhibition constant of s.r. carbonic anhydrase towards acetazolamide was 4-6 X 10(-8) M and similar but not identical to that of cytosolic carbonic anhydrase II. It appears possible that the carbonic anhydrase II-like enzyme previously found by us in muscle homogenates (Siffert & Gros, 1982) originates from the s.r. Histochemical studies using the dansylsuphonamide method described previously (Dermietzel, Leibstein, Siffert, Zamboglou & Gros, 1985) showed an intracellular pattern of carbonic anhydrase staining compatible with the presence of the enzyme in s.r.: spots homogeneously distributed across the fibre cross-sections in transversely sectioned fibres and thin, longitudinally oriented, bands in longitudinally sectioned fibres. It is estimated that s.r. carbonic anhydrase accelerates CO2 hydration within the s.r. approximately 1000-fold. Thus, CO2 and HCO3- react fast enough to provide a rapid source and sink for protons leaving and entering the s.r. in exchange for Ca2+.
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PMID:Carbonic anhydrase in the sarcoplasmic reticulum of rabbit skeletal muscle. 293 36

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

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

Acetate oxidation by sulphate was studied with desulfobacter postgatei. Cell extracts of the organism were found to contain high activities of the following enzymes: citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, fumarase, malate dehydrogenase and pyruvate synthase. It is concluded that acetate oxidation with sulphate in D. postgatei proceeds via the citric acid cycle with the synthesis of pyruvate from acetyl CoA and CO2 as an anaplerotic reaction. The apparent Ks for acetate oxidation by D. postgatei as determined in vivo was near 0.2 mM. The apparent Ks for acetate fermentation to methane and CO2 by methanosarcina barkeri was 3 mM. The significantly lower ks for acetate of the sulphate reducer explains why methane formation from acetate in natural habitats is apparently inhibited by sulphate.
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PMID:Dissimilatory sulphate reduction with acetate as electron donor. 612 36

Three measures of locomotory performance and a series of variables thought to affect performance were measured in the iguanid lizard Ctenosaura similis. Burst speed is mass independent; however, endurance time at 1 km/h (EN-DUR) and maximal distance run (MAX DIS) scale as M0.3. Standard and maximal rates of O2 consumption (VO2max) scale as M0.9; VO2max averages 10-fold greater than standard metabolic rate (SMR). Three of ten enzyme activities measured exhibit significant scaling. After statistically removing the effects of body mass, multiple-regression analysis indicates that 1) 89% of the residual variation in ENDUR is correlated with variation among individuals in thigh muscle mass, VO2max, heart mass, and liver citrate synthase (CS) activity; 2) maximal CO2 consumption (VCO2max) and thigh pyruvate kinase activity statistically explain 64% of the variation in MAX DIS; 3) heart and liver masses together predict 35% of the variation in SMR; 4) thigh and liver CS activity, heart lactate dehydrogenase (LDH) activity, and hematocrit account for 67% of the variation in VO2max;5) 97% of the variation in VCO2max is statistically related to variation in liver CS activity, thigh and heart masses, and heart LDH activity.
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PMID:Physiological correlates of locomotory performance in a lizard: an allometric approach. 623 43

The concentration of metabolically active (i.e. 'free') oxaloacetate in the mitochondrial compartment of isolated liver cells was investigated by two independent approaches. On the basis of mitochondrial aspartate aminotransferase maintaining equilibrium and the direct measurements of mitochondrial aspartate, 2-oxoglutarate and glutamate, the concentration of free oxaloacetate was calculated to be 5 microM after incubation of hepatocytes in the presence of 1.5 mM-lactate and 0.05 mM-oleate. Gradually increasing oleate up to 0.5 mM decreased the free oxaloacetate to 2 microM. Very similar results were obtained when free oxaloacetate concentration was derived from the CO2 production of hepatocytes as a measure of citrate flux through the tricarboxylic acid cycle, and the kinetic data on citrate synthase in situ. The decrease in free oxaloacetate on increasing oleate concentration was associated with lowered rates of cycle-dependent CO2 output and O2 uptake, indicating a decrease in the disposal of acetyl-CoA into the tricarboxylic acid cycle. This decrease could explain 25-30% of the increase in ketone-body production occurring at elevated fatty acid supply. This work documents on a quantitative basis the role of free oxaloacetate in the regulation of ketogenesis.
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PMID:Concentration of free oxaloacetate in the mitochondrial compartment of isolated liver cells. 642 54

Similarities in morphology between copper-deficient cartilage and abnormal cartilage associated with tibial dyschondroplasis (TD) led to studies dealing with copper metabolism and its possible relation to TD. Abnormal cartilage and copper deficient cartilage cells both oxidize significantly less glucose to CO2 and water when compared to normal epiphyseal and day-old hypertrophic cartilage cells. Plasma ceruloplasmin levels and cartilage copper content were not different between normal birds and those affected wth TD, which seemed to rule out a genetic defect in copper metabolism as being partly responsible for the abnormal cartilage occurrence. Mitochondrial marker enzyme activities were investigated, and abnormal cartilage showed a significant decrease in activity of both cytochrome oxidase and citrate synthase. The yield of mitochondria on a percent of total activity basis was quite low from both normal and abnormal cartilages, and, thus, an absolute conclusion with regard to mitochondrial impairment cannot be made at this time.
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PMID:Metabolism of abnormal cartilage cells associated with tibial dyschondroplasia. 741 92

The results from the experiments performed with a mutant deficient in citrate synthase activity can be summarized as follows. (1) Totally blocking entry into the TCA cycle did not appreciably alter the cellular ATP yield. The unchanged yield suggests that for growth on abundant glucose, the sensitivity of ATP yield to TCA cycle flux is low. ATP production in the mutant is altered, in part, by modulating the relative amounts of formate and acetate produced. (2) The in vivo operation of pyruvate-formate lyase and malic enzyme corresponds to proposals developed from in vitro studies. Namely, pyruvate activates the former, and acetyl CoA inhibits the latter. Overall, the diversion of pyruvate to formate under aerobic conditions constitutes an adaptation of the mutant to the enzymatic lesion. The low alpha-ketoglutarate dehydrogenase flux estimated for the mutant indicates that the enzyme is highly repressed in cells growing rapidly on glucose, which is in accord with prior induction-repression studies. Moreover, the lack of a change in uptake flux during the bulk of batch growth is consistent with prior induction-repression studies. (3) The mutant exhibits a heightened sensitivity to CO2 as compared to wild-type counterparts. Growth rate is increased, and the production of formate, malate, glycerate, and pyruvate is reduced. This sensitivity illustrates that citrate synthase is more than an expendable component in an amphibolic pathway. Its presence in wild-type cells "immunizes" against the effect of CO2 fluctuations. (4) The effects of CO2 can be tentatively explained by assuming that the PEP carboxylase-catalyzed reaction is stimulated.
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PMID:Flux adaptations of citrate synthase-deficient Escherichia coli. 783 22

Recent studies indicate that the mucosa of the urinary bladder may play a major role in the maintenance of normal bladder function. The mucosal surface of the urinary bladder serves as a protective layer against the irritative solutes found in the urine. The integrity of this barrier can be broken by overdistension, anoxia, detergents, alcohols, bacterial infection and by contact with agents to which the mucosa has been sensitized. In view that both anoxia and ischemia can mediate a breakdown in the role of the mucosal layer as a permeability barrier, it is reasonable to assume that this function is dependent on cellular metabolism. As an initial investigation we have compared a variety of biochemical and metabolic parameters between the mucosal layer (consisting of the lamina propria, urothelium, and any connective tissue and vascular tissue within this layer); and the muscularis layer. The results of these studies demonstrated that the rate of glucose metabolism to lactic acid (LA) of the mucosa was more than three-fold greater than that of the smooth muscle. The rate of CO2 production of the mucosa was 60% greater than that of the unstimulated smooth muscle. The maximal activity of the mitochondrial enzyme citrate synthase was significantly greater in the mucosa than in the smooth muscle, however, the activity of malate dehydrogenase was similar for both tissues. The maximal activity of the cytosolic enzyme creatine kinase was more than two-fold greater in the bladder smooth muscle than in the mucosa; although the affinities of the creatine kinase isoforms of the mucosa were significantly greater than those of the muscle.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolic studies on rabbit bladder smooth muscle and mucosa. 826 70

Erectile function (erection and detumescence) involves the complex interaction of direct neuronal stimulation of corporal smooth muscle, neurohumoral release of specific endothelial contractile and relaxant factors, and secondary modulation by a variety of putative neuropeptides and vasoactive modulators. The net result is a rapid and sustained relaxation of the smooth muscle elements during erection and contraction of the smooth muscle during detumescence. Proper function of the corporal tissue is dependent upon cellular metabolism of glucose and the generation of cellular energy in the form of high energy phosphates. The current study characterizes the following metabolic parameters of the rabbit corpus cavernosum: Tissue concentrations of creatine phosphate (CP), ATP, ADP, and AMP; maximal rate of glucose metabolism to lactic acid and CO2; and activities of the enzymes creatine kinase (CK), citrate synthase, and malate dehydrogenase. For comparative purposes only, bladder smooth muscle preparations were analyzed simultaneously with and under the same conditions as the corpus cavernosum. The results are as follows: The concentrations of ATP and CP in the corpora were significantly lower than the concentrations in bladder. In the corpora, the tissue concentration of CP was lower than the tissue concentration of ATP, whereas the concentration of CP in the bladder was higher than the concentration of ATP. The rate of glucose metabolism to lactic acid and to carbon dioxide was similar for both bladder smooth muscle and corpus cavernosum. The maximal enzymatic activity of the mitochondrial enzyme citrate synthase was similar for both tissues; similarly, there was no significant difference in the activity of malate dehydrogenase between the two tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolic studies on the rabbit corpus cavernosum. 828 87


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