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)

Muscle biopsies were obtained from three cyclists and four runners at the end of 10-24 mo of intensive training and after intervals of detraining up to 12 wk. Control samples came from four untrained persons and four former athletes. Macro mixed fiber samples were assayed for lactate dehydrogenase, adenylate kinase, glycogen phosphorylase, citrate synthase, malate dehydrogenase, beta-hydroxyacyl-CoA dehydrogenase, succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, creatine kinase, hexokinase, 1-phosphofructokinase, fructosebisphosphatase, protein, and total creatine. In the case of three trained persons and two controls, the first six of the enzymes were also measured in individual fibers. Before detraining, enzymes of oxidative metabolism were substantially higher than in controls, and differences in levels between type I and type II fibers were smaller. During detraining, oxidative enzymes were decreased in both fiber types but the type II fibers did not fall to control levels even after 12 wk. Phosphorylase increased with detraining in both fiber types. The same is true for lactate dehydrogenase and adenylate kinase, except in the case of the type I fibers of one individual. Among the other six enzymes (measured in mixed fiber samples), only hexokinase was consistently affected (decreased) by detraining.
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PMID:Effects of detraining on enzymes of energy metabolism in individual human muscle fibers. 682 50

Individual members of the creatine kinase isoenzyme family (CK; EC 2.7.3.2), which play a prominent role in energy homeostasis, are encoded by four separate nuclear genes. We have isolated and characterized the complete mouse UbCKmit gene, the product of which is ubiquitously expressed and is located in the intermembrane space of mitochondria. Transcription of this gene is initiated at multiple adjacent positions and the region immediately upstream of these sites shares many features with genes encoding housekeeping proteins. These include a high G/C content, absence of TATA and CCAAT motifs, and presence of SP1 and AP2 recognition sequences. In addition, a binding site for HIP1, hormone-responsive elements, and three Mt-motifs, known as boxes shared between nuclear genes encoding mitochondrial proteins, were identified. To study the functional role of the UbCKmit protein, we have inactivated both UbCKmit alleles in mouse embryonic stem (ES) cells. UbCKmit-deficient cells, obtained by consecutive rounds of gene targeting using homologous recombination and drug selection-driven gene conversion events, show no obvious growth disadvantage or abnormal differentiation potential. Activities of mitochondrial cytochrome c oxidase and citrate synthase, as well as the rate of pyruvate oxidation, showed values equal to wild-type cells, indicating a normal aerobic metabolism. Mitochondria of in vivo differentiated knock-out cells were structurally intact, as demonstrated by electron microscopy. Approaches to study the role of the UbCKmit gene further are discussed.
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PMID:Mouse ubiquitous mitochondrial creatine kinase: gene organization and consequences from inactivation in mouse embryonic stem cells. 759 9

The purpose of the study was to verify the influence of several weeks of chronic low-frequency electrical stimulation (LFES) on the metabolic profile and functional capacity of human skeletal muscle. Knee extensor muscles (KEM) of eight subjects were electrically stimulated at 8 Hz for 8 h/day and 6 days/wk. Vastus lateralis muscle samples were taken before, after 4 wk, and after 8 wk of LFES, and activities of anaerobic (creatine kinase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase) and aerobic-oxidative (citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, cytochrome-c oxidase) enzyme markers were determined. KEM dynamic performance was also assessed before, after 4 wk, and after 8 wk of LFES. Activity levels of anaerobic enzymes were not altered, whereas the activity levels of citrate synthase (29%),3-hydroxyacyl-CoA dehydrogenase (22%), and cytochrome-c oxidase (25%) were significantly increased after 4 wk of LFES but were not further increased after 4 additional wk of LFES. KEM performance was also improved (P < 0.05) but leveled off after 4 wk of LFES. Although significant changes were observed, the results of the present study suggest that the muscle characteristics investigated in the current study have a limited capacity of adaptation in response to this form of chronic LFES.
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PMID:Human skeletal muscle adaptation in response to chronic low-frequency electrical stimulation. 783 13

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 cat and the rabbit are two of the most popular models for the study of lower urinary bladder function. The cat has been used extensively for in vivo studies of spinal and supra-spinal micturition reflexes. In contrast, the rabbit has been used extensively for the in vitro study of bladder function. Although the cat and rabbit bladders are approximately the same mass, the cat bladder can generate approximately 6 times the intravesical pressure than the rabbit bladder at the same volume (in vitro response to field stimulation). In order to determine if the increased pressure generation is related to increased cellular energetics, we compared the intracellular concentrations of ATP and creatine phosphate (CP), and the enzyme activities of three enzymes which have important functions in cellular energetics: creatine kinase, citrate synthase, and malic dehydrogenase between the cat and rabbit urinary bladder. The results can be summarized as follows: (1) The bladder weight of the cat and rabbit are similar. (2) The isolated cat bladder can generate approximately 6 times the intravesical pressure of the isolated rabbit bladder. (3) The ATP and CP concentrations of the rabbit are significantly greater than the concentrations in the cat bladder. (4) The hydroxyproline concentration is significantly greater in the cat than the rabbit. (5) The maximum activities of creatine kinase, citrate synthase, and malic dehydrogenase are significantly lower in the cat than the rabbit. In general, it is clear that the ability of the cat to generate high intravesical pressures is not correlated with increased tissue high energy phosphate concentrations, or high enzymatic activities of three specific cytosolic or mitochondrial enzymes.
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PMID:Comparative biochemical characteristics of the cat and rabbit urinary bladder. 792 Jun 87

Mice were treated for 7-12 wk with the creatine analogue beta-guanidinopropionic acid (beta-GPA). Treatment reduced total creatine to approximately 5% of control values in soleus (SOL) and extensor digitorum longus (EDL) muscles. In both muscles from treated mice, phosphorylated beta-GPA accumulated and resting [ATP] decreased by approximately 50%. Relative to controls, cytochrome oxidase and citrate synthase activities increased significantly in EDL from treated mice, but not in SOL; creatine kinase activity decreased significantly in SOL, but not in EDL. Measurements of poststimulation energy metabolism show that the energy cost to maintain tension in SOL and EDL from treated mice was approximately 50% of that in control muscle. Relative to controls, first-order rate constants of poststimulation O2 demand were 2- and 3.6-fold greater in SOL and EDL, respectively, from treated mice. Increased economy of SOL and EDL from treated mice is consistent with previously reported changes in myosin isoenzymes. Increases in rate constants of O2 utilization in creatine-depleted muscle are inconsistent with the hypothesis that cytoplasmic or mitochondrial creatine kinase is rate limiting for cellular respiration.
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PMID:Contractile economy and aerobic recovery metabolism in skeletal muscle adapted to creatine depletion. 804 75

A low metabolic rate for a given body size and a low fat versus carbohydrate oxidation ratio are known risk factors for body weight gain, but the underlying biological mechanisms are poorly understood. Twenty-four-hour energy expenditure (24EE), sleeping metabolic rate (SMR), 24-hour respiratory quotient (24RQ), and forearm oxygen uptake were compared with respect to the proportion of skeletal muscle fiber types and the enzyme activities of the vastus lateralis in 14 subjects (seven men and seven women aged 30 +/- 6 years [mean +/- SD], 79.1 +/- 17.3 kg, 22% +/- 7% body fat). The following enzymes were chosen to represent the major energy-generating pathways: lactate dehydrogenase (LDH) and phosphofructokinase (PFK) for glycolysis; citrate synthase (CS) and beta-hydroxyacl-coenzyme A dehydrogenase (beta-OAC) for oxidation; and creatine kinase (CK) and adenylokinase (AK) for high-energy phosphate metabolism. Forearm resting oxygen uptake adjusted for muscle size correlated positively with the proportion of fast-twitch muscle fibers (IIa: r = .55, P = .04; IIb: r = .51, P = .06) and inversely with the proportion of slow oxidative fibers (I: r = -.77, P = .001). 24EE and SMR adjusted for differences in fat-free mass, fat mass, sex, and age correlated with PFK activity (r = .56, P = .04 and r = .69, P = .007, respectively). 24RQ correlated negatively with beta-OAC activity (r = -.75, P = .002). Our findings suggest that differences in muscle biochemistry account for part of the interindividual variability in muscle oxygen uptake and whole-body energy metabolism, ie, metabolic rate and substrate oxidation.
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PMID:Whole-body energy metabolism and skeletal muscle biochemical characteristics. 815 8

Muscle biopsies of the vastus lateralis muscle taken before and after 18 weeks of resistance training were compared by preparing frozen cross sections for electron microscopy and using adjacent sections for fiber typing by myosin ATPase activity. Quantitative ultrastructural changes were observed in histochemically-identified muscle fiber types of twelve young women who underwent the training. The percentage of type IIB fibers decreased and IIA fibers increased. The cross-sectional area of all major fiber types increased with training. The absolute volume of myofibrils, intermyofibrillar space, and mitochondria increased with training for most major fiber types (type I, IIA and IIAB), but the relative volume percentages were not significantly changed because of corresponding fiber hypertrophy. Mean mitochondrial size for types I and IIA and myofibril size for types IIC and IIB increased significantly with training. The capillary number per fiber and density did not change with training. Activity levels were measured for selected glycolytic and oxidative enzymes. Cytochrome oxidase and hexokinase increased significantly with training, while creatine kinase, citrate synthase, phosphofructokinase, glyceraldehyde phosphate dehydrogenase and hydroxyacyl CoA dehydrogenase enzymes were not significantly altered. The results suggest that this type of high-repetition resistance training causes the intracellular components of all fiber types to increase proportionally with an increase in fiber size. In addition, the enzyme analysis indicates the muscle as a whole may increase its oxidative phosphorylation capacity in conjunction with the decreased percentage of type IIB fibers.
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PMID:Muscle fiber types of women after resistance training--quantitative ultrastructure and enzyme activity. 825 33

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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