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)

We investigated age-related changes in antioxidant, glycolytic, beta-oxidation, and tricarboxylic acid cycle enzyme activity in the diaphragm and plantaris muscle of female Fischer 344 rats. Tissue samples from the costal and crural diaphragm and plantaris muscle were obtained from 30 animals in the following age groups: 1) 6 mo old (n = 10), 2) 26 mo old (n = 10), and 3) 30 mo old (n = 10). Aging had no effect (P greater than 0.05) on the activities of citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HADH) in the costal or crural diaphragm. Similarly, no age-related differences existed (P greater than 0.05) in the crural diaphragm in lactate dehydrogenase (LDH) or glutathione peroxidase (GPX) activity. In contrast, the activities of LDH and GPX were significantly (P less than 0.05) higher in the costal diaphragm in the 30- than in the 6-mo old animals. In addition, the ratio of LDH to CS activity increased (P less than 0.05) as a function of age in the costal diaphragm. Conversely, the ratio of CS to GPX activity in the costal diaphragm was lower (P less than 0.05) in the 30- than in the 6-mo old animals. No significant (P greater than 0.05) age-related differences existed in LDH-to-CS or CS-to-GPX activity ratios in the crural diaphragm. Finally, aging resulted in a significant decrease (P less than 0.05) in the activities of LDH, CS, and HADH in the plantaris muscle. These data demonstrate that, unlike many hindlimb locomotor muscles, the oxidative capacity of the Fischer 344 rat diaphragm does not decrease in old age.
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PMID:Alterations in diaphragmatic oxidative and antioxidant enzymes in the senescent Fischer 344 rat. 162 87

1. Activities of a glycolytic enzyme--lactate dehydrogenase, LDH, and two oxidative enzymes--citrate synthase (CS), a marker for TCA cycle entry, and 3-hydroxyacyl-CoA dehydrogenase (HAD), which indicates the capacity for beta-oxidation of endogenous lipids, were measured in fast (tibialis anterior, TA, and extensor digitorum longus, EDL) and slow (soleus, SOL) muscles of Sprague-Dawley rats with intact and limited blood supply, and following treatment with the xanthine derivative torbafylline (Hoechst, Werk Albert, Wiesbaden). 2. Limitation of blood supply by unilateral ligation of the common iliac artery increased activity of LDH in fast muscles, and activity of CS and HAD in soleus. 3. Torbafylline treatment caused an increased LDH activity in intact fast muscles and decreased it in soleus, although the relative capacity for anaerobic and aerobic metabolism (indicated by the ratio of LDH and CS activities) remained unchanged in all cases. 4. Whilst having little effect on oxidative enzyme activity of fast muscles, torbafylline decreased the activity of CS but increased activity of HAD in soleus, suggesting a greater reliance on lipid metabolism. 5. The effect of arterial ligation on enzyme activity was ameliorated by treatment with torbafylline, possibly due to its effect on the microcirculation.
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PMID:The effect of torbafylline on enzyme activities in fast and slow muscles with limited blood supply. 167 66

Maximal in vitro activities of key metabolic enzymes were measured in brain and eye heaters of five species of scombroid fishes. Istiophorid billfishes (blue marlin, striped marlin and Mediterranean spearfish), xiphiid billfishes (Pacific and Mediterranean stocks) and a scombrid fish (butterfly mackerel) were included in the analysis. Our main objectives were (1) to assess the maximum possible substrate flux in heater tissue, and (2) to determine what metabolic substrates could fuel heat production. Heater tissue of all scombroids examined showed extremely high oxidative capacity. Activities of citrate synthase, a commonly measured index of oxidative metabolism, included the highest value ever reported for vertebrate tissue. In most billfishes, citrate synthase activities were similar to or higher than those found for mammalian cardiac and avian flight muscle. Marker enzymes for aerobic carbohydrate metabolism (hexokinase) and fatty acid metabolism (carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase) also displayed extraordinarily high activities. Activities of carnitine palmitoyltransferase measured in heater organs were among the highest reported for vertebrates. These results indicate that heat production could be fueled aerobically by either lipid or carbohydrate metabolism. Inter- and intraspecifically, heater organs of fishes from the colder Mediterranean waters had a higher aerobic capacity and, hence, a greater heat-generating potential, than fishes from the warmer waters of the Pacific. This difference may be attributed to different thermal environments or it may result from allometry, since fishes caught in the Mediterranean were considerably smaller than those caught in the Pacific.
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PMID:Activities of key metabolic enzymes in the heater organs of scombroid fishes. 175 72

The purpose was to determine the biochemical and hemodynamic adaptations of the myocardium to chronic tachycardia. Cardiac pacemakers were implanted in Yorkshire pigs and set at a rate of 180 beats/min for a period of 35-42 days. Animals were then anesthetized with pentobarbital sodium. Myocardial blood flow and hemodynamics were determined at three different heart rates (i.e., 120, 180, and 220 beats/min). Tissue samples were then taken for microsphere and biochemical analyses. Chronically paced hearts maintained better cardiac function and had consistently higher left ventricular blood flow with a higher endocardial-to-epicardial ratio. The activities of citrate synthase and 3-hydroxyacyl-CoA dehydrogenase were 23 and 45% greater in the paced hearts, respectively. The sarcoplasmic reticulum adenosinetriphosphatase activity was 55% greater in the paced hearts, whereas the myosin adenosinetriphosphatase was the same as in the control hearts. Polyacrylamide gels of the ventricular myosin isoforms showed only the V3 type to be present in both the control and paced hearts. These findings show that the heart of a large mammal adapts to chronic tachycardia (i.e., 180 beats/min) by elevating the aerobic and calcium-sequestering capacities without altering its myosin type.
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PMID:Myocardial biochemical and hemodynamic adaptations to chronic tachycardia. 182 10

The purpose of this study was to determine whether cardiac biochemical adaptations are induced by chronic exercise training (ET) of miniature swine. Female Yucatan miniature swine were trained on a treadmill or were cage confined (C) for 16-22 wk. After training, the ET pigs had increased exercise tolerance, lower heart rates during exercise at submaximal intensities, moderate cardiac hypertrophy, increased coronary blood flow capacity, and increased oxidative capacity of skeletal muscle. Myosin from both the C and ET hearts was 100% of the V3 isozyme, and there were no differences between the myosin adenosine triphosphatase (ATPase) or myofibrillar ATPase activities of C and ET hearts. Also, the sarcoplasmic reticulum Ca(2+)-ATPase activity and Na(+)-Ca2+ exchange activity of sarcolemmal vesicles were the same in cardiac muscle of C and ET hearts. Finally, the glycolytic and oxidative capacity of ET cardiac muscle was not different from control, since phosphofructokinase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase activities were the same in cardiac tissue from ET and C pigs. We conclude that endurance exercise training does not provide sufficient stress on the heart of a large mammal to induce changes in any of the three major cardiac biochemical systems of the porcine myocardium: the contractile system, the Ca2+ regulatory systems, or the metabolic system.
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PMID:Biochemical characterization of exercise-trained porcine myocardium. 183 67

This study was conducted to obtain additional information about the adaptations after 12 wk of high-fat diet (HFD) per se or HFD combined with endurance training in the rat using a two [diet: carbohydrate (CHO) or HFD] by two (training: sedentary or trained) by two (condition at death: rested or exercised) factorial design. Adaptation to prolonged HFD increases maximal O2 uptake (VO2max; 13%, P less than 0.05) and submaximal running endurance (+64%, P less than 0.05). This enhancement in exercise capacity could be attributed to 1) an increase in skeletal muscle aerobic enzyme activities (3-hydroxyacyl-CoA dehydrogenase and citrate synthase in soleus and red quadriceps) or 2) a decrease in liver glycogen breakdown in response to 1 h exercise at 80% VO2max. When training is superimposed to HFD, the most prominent finding provided by this study is that the diet-induced effects are cumulative with the well-known training effect on VO2max, exercise endurance, oxidative capacity of red muscle, and metabolic responses to exercise, with a further reduction in liver glycogen breakdown.
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PMID:Additive effects of training and high-fat diet on energy metabolism during exercise. 191 43

Fast-twitch tibialis anterior muscle of the rabbit was subjected to chronic low-frequency (10 Hz, 10 h/day) stimulation for different time periods up to 28 days. Total cellular activities of carnitine:palmitoyl-CoA transferase, crotonase, 3-hydroxyacyl-CoA dehydrogenase, 3-keto-acyl-CoA thiolase, citrate synthase, NADH:cytochrome c oxidoreductase, succinate: cytochrome c oxidoreductase, and cytochrome c oxidase were measured in contralateral and stimulated muscles at various times. With the exception of crotonase, which increased only 1.6-fold after 28 days of stimulation, the other enzymes increased in parallel displaying 3-fold elevated absolute activities. These results, by supporting and extending our previous findings, indicate that the expression of the enzymes of the main metabolic systems of aerobic substrate oxidation, i.e. the citric acid cycle, the fatty acid oxidation and the respiratory chain, is regulated in a coordinate manner.
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PMID:Enzyme activities of fatty acid oxidation and the respiratory chain in chronically stimulated fast-twitch muscle of the rabbit. 194 50

Eleven enzymes were measured in individual fibers of soleus and tibialis anterior (TA) muscles from two flight and two control (synchronous) animals. There were five enzymes of glycogenolytic metabolism: phosphorylase, glucose-6-phosphate isomerase, glycerol-3-phosphate dehydrogenase, pyruvate kinase, and lactate dehydrogenase (group GLY); five of oxidative metabolism: citrate synthase, malate dehydrogenase, beta-hydroxyacyl-CoA dehydrogenase, 3-ketoacid CoA-transferase, and mitochondrial thiolase (group OX); and hexokinase, subserving both groups. Fiber size (dry weight per unit length) was reduced about 35% in both muscles. On a dry weight basis, hexokinase levels were increased 100% or more in flight fibers from both soleus and TA. Group OX enzymes increased 56-193% in TA without significant change in soleus. Group GLY enzymes increased an average of 28% in soleus fibers but underwent, if anything, a modest decrease (20%) in TA fibers. These changes in composition of TA fibers were those anticipated for a conversion of about half of the originally predominant fast glycolytic fibers into fast oxidative glycolytic fibers. Calculation on the basis of fiber length, rather than dry weight, gave an estimate of absolute enzyme changes: hexokinase was still calculated to have increased in both soleus and TA fibers, but only by 50 and 25%, respectively. Three of the OX enzymes were, on this basis, unchanged in TA fibers, but 3-ketoacid CoA-transferase and thiolase had still nearly doubled, whereas TA GLY enzymes had fallen about 40%. In soleus fibers, absolute levels of OX enzymes had decreased an average of 25% and GLY enzymes were marginally decreased.
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PMID:Effect of microgravity on metabolic enzymes of individual muscle fibers. 196 37

The purpose of this study was to determine the extent to which functional demand regulates the biochemical character and enzyme capacities of the rat myocardium. Hearts from donor rats were heterotopically transplanted onto the abdominal aorta and inferior vena cava of isogenic recipients. The procedure results in a perfused but nonpumping heart that has a reduced heart rate (HR) and performs essentially no stroke work (SW). After 30 days, metabolic enzyme activities (phosphorylase, 6-phosphofructokinase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase) were significantly lower (40-60%) in the nonworking heart. Specific sarcoplasmic reticulum Ca2(+)-adenosinetriphosphatase (ATPase) activity was unchanged, but activity per gram of heart was 41% lower. Myosin isozymes were 58% V1, 21% V2, and 21% V3 in the nonworking heart compared with 100% V1 in the working heart. Myosin and myofibrillar ATPase activities each decreased by 28%. These findings suggest that both HR and SW play major and specific roles in regulating myocardial biochemical capacities and determining the myosin phenotype.
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PMID:Role of cardiac work in regulating myocardial biochemical characteristics. 214 21

Skeletal muscle has an inherent biochemical phenotypic plasticity that provides the possibility for it to be remodeled into a "heart-like" muscle for use in cardiac-assist devices. The purpose of this study was to chronically stimulate skeletal muscle electrically to transform the biochemical capacities of the three major subcellular systems (i.e., metabolic, calcium regulating, and contractile) to resemble those of heart muscle. The latissimus dorsi muscle (LDM) of mongrel dogs weighing 22-27 kg was stimulated via the thoracodorsal nerve at 2 Hz for 6-8 wk. This stimulation protocol reduced the phosphorylase (glycogenolytic) and phosphofructokinase (glycolytic) activities by 70%. The aerobic (citrate synthase activity) and fatty acid oxidative (3-hydroxyacyl-CoA dehydrogenase activity) capacities were not significantly increased by chronic stimulation and remained at about one-fourth those in the canine heart. The calcium-dependent sarcoplasmic reticulum adenosinetriphosphatase (ATPase) activity in the microsomal fraction, which was sixfold greater in the nonstimulated LDM than in the heart, was reduced by electrical stimulation to a level similar to that of the dog heart. The contractile capacity was evaluated by determining the percentage of types I and II fibers, the myofibrillar ATPase activity, and the proportion of myosin isoforms. The transformed muscle was comprised of 93 +/- 2% type I fibers, a myofibrillar ATPase activity similar to that in heart with primarily a slow-twitch muscle myosin isoform. In conclusion, electrical stimulation of canine LDM at 2 Hz for 6-8 wk resulted in two of the three biochemical systems, which confer physiological expression and fatigue resistance to muscle being transformed to resemble those of the myocardium.
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PMID:Biochemical transformation of canine skeletal muscle for use in cardiac-assist devices. 214 Aug 28


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