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

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

A new, sensitive assay for the quantitative determination of AMP deaminase activity in human skeletal muscle is presented. The method is based on the determination of the direct product of the AMP deaminase reaction, the formed IMP, by high performance liquid chromatography (HPLC). In order to evaluate the relationship between AMP deaminase activity on the one hand and the contractile and metabolic characteristics of the muscle and the physical performance on the other, muscle biopsies were taken from 20 male subjects. The subjects also performed a 30 s sprint test on a cycle ergometer. The inter-individual variation in AMP deaminase activity was large, ranging from 5.4 to 27.4 microkat g-1 dry muscle. AMP deaminase was positively correlated with phosphofructokinase (PFK), the marker of the glycolytic capacity of the muscle, but there was no correlation with enzymes of oxidative metabolism, such as 3-hydroxyacyl-CoA dehydrogenase and citrate synthase, or with the activity of myokinase and lactate dehydrogenase. There was no significant correlation between AMP deaminase activity and the proportion of the different muscle fibre types. A weak positive correlation was found between the sprint performance and the AMP deaminase activity. In conclusion, the HPLC assay was found to be a fast, sensitive and reliable method for the quantitative determination of AMP deaminase activity in muscle. A direct relationship between AMP deaminase activity on the one hand and glycolytic capacity and sprint performance on the other was found. However, no relationship to oxidative capacity or contractile properties was found.
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PMID:AMP deaminase in skeletal muscle of healthy males quantitatively determined by new assay. 803 9

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

The conditions of treatment of human skeletal muscle fibers from M. vastus lateralis with saponin were optimized to achieve complete permeabilization of cell membrane at intact mitochondrial oxidative phosphorylation. After 30 min of incubation with saponin all lactate dehydrogenase, 50% of creatine kinase, 30% of adenylate kinase and less than 20% of citrate synthase was released into the permeabilization medium. These skinned fibers behave similar to isolated mitochondria from human skeletal muscle: (i) the respiration with mitochondrial substrates can be stimulated by ADP, (ii) inhibited by carboxyatractyloside and (iii) it is possible to detect fluorescence changes of mitochondrial NAD(P)H on additions of substrates, uncoupler and cyanide. From a comparison of rates of respiration per cytochrome aa3 content of isolated human skeletal muscle mitochondria and saponin-skinned muscle fibers it was possible to calculate that almost 85% of mitochondria in those fibers are accessible for the investigation of oxidative phosphorylation. As shown by the investigation of biopsy samples of two patients with undefined myopathies these fibers are a suitable object for the replacement of isolated mitochondria in the diagnosis of mitochondrial myopathies and encephalomyopathies.
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PMID:Functional characterization of mitochondrial oxidative phosphorylation in saponin-skinned human muscle fibers. 834 61

To test whether repeated HBO exposures would increase activity of skeletal muscle metabolic enzymes, 27 rabbits (3 groups) were exposed 90 min/day, 5 days/wk to either 100% O2 at 243 kPa (HBO), 100% O2 at 101 kPa (HIO), or 21% O2 at 101 kPa (CON). Four animals per group were killed after 2 wk treatment, and the remaining five per group were killed after 8 wk of treatment. Soleus, plantaris, and tibialis anterior muscles were removed, and the activities of adenylate kinase, alpha-glycerophosphate dehydrogenase, and citrate synthase were measured. After 8 wk there was no difference in enzyme activity between groups for either plantaris or tibialis anterior. In the soleus after 8 wk there was no difference between groups in adenylate kinase activity, but alpha-glycerophosphate dehydrogenase activity was 56% greater (P < 0.05) in HBO than in HIO and 50% greater than in CON, and citrate synthase activity in HBO was 24% greater (P < 0.05) than that in HIO and 36% greater than that in CON. Inasmuch as the soleus is a postural muscle, these results suggest that long-term HBO treatments can increase enzyme activity in an actively contracting muscle.
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PMID:Skeletal muscle metabolic enzymes are altered by hyperbaric oxygenation treatments. 840 Nov 48

The effect of sprint training and detraining on supramaximal performances was studied in relation to muscle enzyme adaptations in eight students trained four times a week for 9 weeks on a cycle ergometer. The subjects were tested for peak oxygen uptake (VO2peak), maximal aerobic power (MAP) and maximal short-term power output (Wmax) before and after training and after 7 weeks of detraining. During these periods, biopsies were taken from vastus lateralis muscle for the determination of creatine kinase (CK), adenylate kinase (AK), glycogen phosphorylase (PHOS), hexokinase (HK), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and its isozymes, 3-hydroxy-acyl-CoA dehydrogenase (HAD) and citrate synthase (CS) activities. Training induced large improvements in Wmax (28%) with slight increases (3%) in VO2peak (P < 0.10). This was associated with a greater glycolytic potential as shown by higher activities for PHOS (9%), PFK (17%) and LDH (31%) after training, without changes in CK and oxidative markers (CS and HAD). Detraining induced significant decreases in VO2peak (4%), MAP (5%) and oxidative markers (10-16%), while Wmax and the anaerobic potential were maintained at a high level. This suggests a high level in supramaximal power output as a result of a muscle glycogenolytic and glycolytic adaptation. A long interruption in training has negligible effects on short-sprint ability and muscle anaerobic potential. On the other hand, a persistent training stimulus is required to maintain high aerobic capacity and muscle oxidative potential. This may contribute to a rapid return to competitive fitness for sprinters and power athletes.
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PMID:Enzyme adaptations of human skeletal muscle during bicycle short-sprint training and detraining. 942 50

In contrast to endurance training, little research has been carried out to investigate the effects of short (< 10 s) sprint training on performance, muscle metabolism and fibre types. Nine fit male subjects performed a mean of 16 outdoor sprint running training sessions over 6 weeks. Distances sprinted were 30-80 m at 90-100% maximum speed and between 20 and 40 sprints were performed in each session. Endurance (maximal oxygen consumption; VO2max), sprint (10 m and 40 m times), sustained sprint (supramaximal treadmill run) and repeated sprint (6 x 40 m sprints, 24 s recovery between each) performance tests were performed before and after training. Muscle biopsy samples (vastus lateralis) were also taken to examine changes in metabolites, enzyme activities and fibre types. After training, significant improvements were seen in 40 m time (P < 0.01), supramaximal treadmill run time (P < 0.05), repeated sprint performance (P < 0.05) and VO2max (P < 0.01). Resting muscle concentrations of ATP and phosphocreatine did not change. Phosphorylase activity increased (P < 0.025), citrate synthase activity decreased (P < 0.01), but no significant changes were recorded in myokinase and phosphofructokinase activities. The proportion of type II muscle fibres increased significantly (P < 0.05). These results demonstrate that 6 weeks of short sprint training can improve endurance, sprint and repeated sprint ability in fit subjects. Increases in the proportion of type II muscle fibres are also possible with this type of training.
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PMID:Changes in performance, muscle metabolites, enzymes and fibre types after short sprint training. 969 16

Muscle deconditioning is a common observation in patients with congestive heart failure (CHF), chronic obstructive pulmonary disease, neuromuscular diseases or prolonged bed rest. To gain further insight into metabolic and mechanical properties of deconditioned slow-twitch (soleus) or fast-twitch (EDL) skeletal muscles, we induced experimental muscle deconditioning by hindlimb suspension (HS) in rats for 3 weeks. Cardiac muscle was also studied. Besides profound muscle atrophy, increased proportion of fast type II fibers as well as fast myosin isoenzymes, we found decreased calcium sensitivity of Triton X-100 skinned fiber bundles of soleus muscle directed towards the fast muscle phenotype. Glycolytic enzymes such as hexokinase and pyruvate kinase were increased, and the LDH isoenzyme pattern was clearly shifted from an oxidative to an anaerobic profile. Creatine kinase (CK) and myokinase activities were increased in HS soleus towards EDL values. Moreover, the M-CK mRNA level was greatly increased in soleus, with no change in EDL. However, oxygen consumption rate assessed in situ in saponin skinned fibers (12.5 +/- 0.8 in C and 15.1 +/- 0.9 micromol O2/min/g dw in HS soleus compared to 7.3 +/- 1.3 micromol O2/min/g dw in control EDL), as well as mitochondrial CK (mi-CK) and citrate synthase activities, were preserved in HS soleus. Following deconditioning no change in Km for ADP of mitochondrial respiration, either in the absence (511 +/- 92 in C and 511 +/- 111 microM in HS soleus compared to 9 +/- 4 microM in control EDL) or presence of creatine (88 +/- 10 in C and 95 +/- 16 microM in HS soleus compared to 32 +/- 9 microM in control EDL), was found. The results show that muscle deconditioning induces a biochemical and functional slow to fast phenotype transition in myofibrillar and cytosolic compartments of postural muscle, but not in the mitochondrial compartment, suggesting that these compartments are differently regulated under conditions of decreased activity.
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PMID:Muscle unloading induces slow to fast transitions in myofibrillar but not mitochondrial properties. Relevance to skeletal muscle abnormalities in heart failure. 992 74

Oxidative capacity of muscles correlates with capillary density and with microcirculation, which in turn depend on various regulatory factors, including NO generated by endothelial nitric oxide synthase (eNOS). To determine the role of eNOS in patterns of regulation of energy metabolism in various muscles, we studied mitochondrial respiration in situ in saponin-permeabilized fibres as well as the energy metabolism enzyme profile in the cardiac, soleus (oxidative) and gastrocnemius (glycolytic) muscles isolated from mice lacking eNOS (eNOS(-/-)). In soleus muscle, the absence of eNOS induced a marked decrease in both basal mitochondrial respiration without ADP (-32%; P <0.05) and maximal respiration in the presence of ADP (-29%; P <0.05). Furthermore, the eNOS(-/-) soleus muscle showed a decrease in total creatine kinase (-29%; P <0.05), citrate synthase (-31%; P <0.01), adenylate kinase (-27%; P <0.05), glyceraldehyde-3-phosphate dehydrogenase (-43%; P <0.01) and pyruvate kinase (-26%; P <0.05) activities. The percentage of myosin heavy chains I (slow isoform) was significantly increased from 24.3+/-1.5% in control to 30.1+/-1.1% in eNOS(-/-) soleus muscle ( P <0.05) at the expense of a slight non-significant decrease in the three other (fast) isoforms. Besides, eNOS(-/-) soleus showed a 28% loss of weight. Interestingly, we did not find differences in any parameters in cardiac and gastrocnemius muscles compared with respective controls. These results show that eNOS knockout has an important effect on muscle oxidative capacity as well on the activities of energy metabolism enzymes in oxidative (soleus) muscle. The absence of such effects in cardiac and glycolytic (gastrocnemius) muscle suggests a specific role for eNOS-produced NO in oxidative skeletal muscle.
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PMID:Endothelial nitric oxide synthase (NOS) deficiency affects energy metabolism pattern in murine oxidative skeletal muscle. 1212 18


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