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)

The degree to which the y-intercept (Y-int) of the linear regression of maximal work output on exercise duration represented anaerobic capacity was determined in ten well-trained male cyclists [peak oxygen uptake (VO2peak) = 69.8 (SD 4.2) ml.kg-1.min-1]. Each cyclist performed three exhausting cycle sessions on separate occasions; the mean exercise durations were 312, 243 and 141 s for the low (approximately 104% VO2peak), medium (approximately 108% VO2peak) and high (approximately 113% VO2peak) intensities respectively, and Y-int (kilojoules; joules per kilogram) was derived from the regression of work output on exercise duration. The muscle anaerobic adenosine 5'-triphosphate (ATP) yield (sigma ATP) and anaerobic capacity (AC) were estimated from changes in metabolites in the vastus lateralis muscle and blood lactate concentration during the high intensity cycling session. The activities of glycogen phosphorylase, phosphofructokinase and citrate synthase, as well as muscle buffer value (in vitro beta) were also determined. The Y-int (kilojoules) was positively correlated (P < or = 0.05) with AC (r = 0.73), sigma ATP (r = 0.70) and in vitro beta (r = 0.71); similar correlations (P < or = 0.05) were observed for Y-int (joules per kilogram). The Y-int was not correlated (P > 0.05) with any enzyme activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Y-intercept of the maximal work-duration relationship and anaerobic capacity in cyclists. 771 77

Skeletal muscle samples were obtained by needle biopsy from two depths of the m. gluteus medius of 50, young race-trained thoroughbred racehorses. Histochemical and biochemical characteristics of the muscle samples were analysed. Fibres were classified as type I, type IIa or type IIb on the basis of the pH dependent lability of the myosin ATPase reaction. The activities of citrate synthase (CS) and glycogen phosphorylase (Phos) were determined. Muscle fibre composition varied markedly between deep and superficial muscle samples and this was reflected in differences in the activities of citrate synthase (CS) and phosphorylase (Phos). CS activity was greater in samples taken from a depth of 90 mm (deep) than those taken from a depth of 40 mm (superficial: 122 +/- 19 compared with 88 +/- 16 mumol/g dry muscle/min at 25 degrees C). Phos activity was greater in superficial samples (137 +/- 20) compared with deep samples (117 +/- 21). Regression analysis was used to estimate the enzyme activities in the different fibre types. No significant correlations were observed between histochemical and biochemical measures and subsequent racing performance.
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PMID:Skeletal muscle characteristics in 2 year-old race-trained thoroughbred horses. 791 52

Selected enzymes were measured in mixed-fiber bundles and individual fibers from rat plantaris (PL) and soleus (Sol) muscles that had undergone either 2 wk of tetrodotoxin (TTX) inactivation of the sciatic nerve, a sham operation, or were contralateral to the TTX limb. TTX disuse caused severe wasting of PL (46%) and Sol (26%) muscles and of single fibers (50% and 40%, respectively). TTX PL and Sol also had reduced (50%) glycogen content. In TTX, PL, and Sol macro samples and single fibers, the activities (mol.h-1.kg dry wt-1) of hexokinase, glycogen phosphorylase, and lactate dehydrogenase were higher, lower, and unchanged, respectively, compared with controls. Single-fiber data showed that these changes occurred in all fibers. In TTX PL macro samples, activities of glycerol-3-phosphate dehydrogenase (GPDH), pyruvate kinase (PK), malate dehydrogenase (MDH), citrate synthase (CS), beta-hydroxyacyl-CoA dehydrogenase (BOAC), and thiolase were, or tended to be, lower. Single-fiber data showed a disappearance of high-oxidative moderate glycolytic fibers (i.e., usually fast-twitch oxidative in control) and the appearance of more fibers with a metabolic enzyme profile approaching that of control slow-oxidative fibers. In TTX Sol macro samples, GPDH and PK tended to be higher, and thiolase, BOAC, CS, and MDH lower. Single-fiber data corroborated these findings and suggested the appearance of fast fibers with downregulated oxidative enzyme profiles. Our results suggest that neuromuscular activity is a major, but not the sole, determinant of the size and metabolic heterogeneity that exists in muscle cells.
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PMID:Effects of tetrodotoxin-induced neural inactivation on single muscle fiber metabolic enzymes. 804 92

Three antischistosomal drugs, praziquantel (CAS 55268-74-1, EMBAY 8440, Prz), oxamniquine (CAS 21738-42-1, Oxa) and oltipraz (CAS 64224-21-1, Olt) were examined for their ability to reverse the disturbances in carbohydrate metabolism induced by Schistosoma mansoni (S. mansoni) infection. The infected mice were screened every 2 weeks for 16 weeks for their body and liver weights in addition to assessment of the activities of liver pyruvate kinase (PK), phosphofructokinase (PFK) (glycolysis), citrate synthase (CS) (Krebs' cycle) glycogen phosphorylase (GP) (glycogenolysis), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) (hexose monophosphate shunt). Results of the study showed that infection with S. mansoni caused the following changes in mice livers: 1. significant increase in liver weights from the 6th week of infection, which coincided with schistosomal egg deposition, whereas body weights were reduced, 2. remarkable increase in the activities of PK and PFK from the 4th week of infection, 3. marked reduction in CS, GP, G6PDH and 6PGDH. These results lead to the conclusion that glycolysis is largely stimulated in the livers of infected mice on the expense of other metabolic pathways of glucose utilization. Administration of Prz to infected mice caused normalization of all measured enzyme activities almost from the 2nd week of infection, whereas liver and body weights were improved from the 10th week. Oxa was less effective in these regards while Olt was the least. These data support the selection of Prz as a drug of choice for S. mansoni infection.
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PMID:Effect of schistosomal infection and its treatment on some key enzymes of glucose metabolism in mice livers. 859 93

Anaerobic ATP production in skeletal muscle and the accumulated oxygen deficit (O2D) incurred during an exhaustive cycle bout (duration = 173 +/- 24 s; intensity = 112 +/- 3% VO2peak), were determined in 10 male cyclists (mean +/- SD: VO2peak = 69.8 +/- 4.2 ml.kg-1.min-1). Anaerobic ATP production (mmol.kg-1 d.w.) was determined from changes in lactate, phosphocreatine, ATP, and ADP in vastus lateralis. Muscle buffer value and the activities of glycogen phosphorylase (PHOS), phosphofructokinase and citrate synthase (CS) were also determined. The anaerobic ATP production determined from measured muscle metabolites was 202.7 +/- 46.9 mmol.kg-1 d.w. and was correlated (P < or = 0.05) with muscle buffer value (r = 0.81), PHOS (r = 0.69) and the ratio of PHOS to CS activity (r = 0.77). The O2D was 55.2 +/- 10.3 ml O2 Eq.kg-1, but was not correlated (P > 0.05) with anaerobic ATP production (r = -0.38), buffer value (r = -0.50) or PHOS (r = -0.39). These latter findings could be explained by error in measuring the O2D and/or muscle anaerobic ATP production in well-trained cyclists.
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PMID:Anaerobic ATP production and accumulated O2 deficit in cyclists. 877 20

The activities of 18 enzymes involved in the intermediary and energy metabolism were measured in certain widely-spread peracarid crustaceans: 3 hypogean (Niphargus virei, Niphargus rhenorhodanensis and Stenasellus virei) and 2 epigean (Gammarus fossarum and Asellus aquaticus) ones. The activities of numerous enzymes were correlated with the known metabolic rates of the 5 species. Such rates are reduced in hypogean organisms: levels of enzymatic activity in subterranean species were 1.2 to 8.6 times lower than in epigean species for the main key regulatory enzymes involved in the Krebs cycle and glycolysis (phosphofructokinase, pyruvate kinase, hexokinase and citrate synthetase). The relative activities of phosphofructokinase, glycogen phosphorylase and hexokinase clearly indicated that glycogen was the main fuel oxidized in both epigean and hypogean organisms. A higher glycogen phosphorylase/hexokinase ratio in hypogean than in epigean crustaceans showed that subterranean species had a greater ability to function anaerobically. The presence of high activities of glutamate-pyruvate transaminase and lactate dehydrogenase in all species (and of malate dehydrogenase and fumarase in hypogean species) was indicative of a coupled fermentation of glycogen and glutamate during anaerobiosis, with lactate and alanine as end-products (as well as succinate in hypogean species). A low fructose-1,6-bisphosphatase/phosphofructokinase ratio, associated with a low level of phosphoenolpyruvate carboxykinase activity, indicated that the glycolytic pathway was active and that gluconeogenic ability was limited in epigean crustaceans. In contrast, in hypogean species, association of a higher ratio and a high level of phosphoenolpyruvate carboxykinase activity suggested a low glycolytic activity and a high gluconeogenic ability.
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PMID:The activities of enzymes associated with the intermediary and energy metabolism in hypogean and epigean crustaceans. 909 Nov 76

The insulin resistance of skeletal muscle in glucose-tolerant obese individuals is associated with reduced activity of oxidative enzymes and a disproportionate increase in activity of glycolytic enzymes. Because non-insulin-dependent diabetes mellitus (NIDDM) is a disorder characterized by even more severe insulin resistance of skeletal muscle and because many individuals with NIDDM are obese, the present study was undertaken to examine whether decreased oxidative and increased glycolytic enzyme activities are also present in NIDDM. Percutaneous biopsy of vatus lateralis muscle was obtained in eight lean (L) and eight obese (O) nondiabetic subjects and in eight obese NIDDM subjects and was assayed for marker enzymes of the glycolytic [phosphofructokinase, glyceraldehyde phosphate dehydrogenase, hexokinase (HK)] and oxidative pathways [citrate synthase (CS), cytochrome-c oxidase], as well as for a glycogenolytic enzyme (glycogen phosphorylase) and a marker of anaerobic ATP resynthesis (creatine kinase). Insulin sensitivity was measured by using the euglycemic clamp technique. Activity for glycolytic enzymes (phosphofructokinase, glyceraldehye phosphate dehydrogenase, HK) was highest in subjects with subjects with NIDDM, following the order of NIDDM > O > L, whereas maximum velocity for oxidative enzymes (CS, cytochrome-c oxidase) was lowest in subjects with NIDDM. The ratio between glycolytic and oxidative enzyme activities within skeletal muscle correlated negatively with insulin sensitivity. The HK/CS ratio had the strongest correlation (r = -0.60, P < 0.01) with insulin sensitivity. In summary, an imbalance between glycolytic and oxidative enzyme capacities is present in NIDDM subjects and is more severe than in obese or lean glucose-tolerant subjects. The altered ratio between glycolytic and oxidative enzyme activities found in skeletal muscle of individuals with NIDDM suggests that a dysregulation between mitochondrial oxidative capacity and capacity for glycolysis is an important component of the expression of insulin resistance.
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PMID:Altered glycolytic and oxidative capacities of skeletal muscle contribute to insulin resistance in NIDDM. 921 60

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

Mammalian hibernation requires specific regulatory controls on metabolism to coordinate entry, maintenance, and arousal stages, as well as adjustments to many metabolic functions to support long-term dormancy. Several mechanisms of metabolic regulation are involved in potentiating survival. One of these is the reversible phosphorylation of regulatory enzymes, including glycogen phosphorylase, phosphofructokinase, pyruvate kinase, and pyruvate dehydrogenase. In particular, the sharp suppression of pyruvate dehydrogenase during hibernation shows the importance of control over mitochondrial oxidative metabolism for reducing metabolic rate. Fine control over specific enzymes also occurs via differential temperature effects on kinetic and allosteric properties. Analysis of temperature effects on the properties of pyruvate kinase, fructose-1,6-bisphosphatase, creatine kinase, and citrate synthase from ground squirrel or bat tissues shows a range of responses, some that would reduce enzyme activity in the hibernating state and some that would promote temperature-insensitive enzyme function. Reduced tissue phosphagen and adenylate levels, but not energy charge, may also contribute to overall metabolic suppression. New research is exploring the role of transcriptional and translational controls in hibernation via several approaches. For example, immunoblotting with antibodies to heat shock proteins (hsp 70 family) revealed the presence of constitutive hsc 70 in bat tissues but levels of the protein did not change between euthermic and hibernating states and neither the inducible hsp 70 nor the glucose-responsive protein grp 78 appeared during hibernation.
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PMID:Metabolic regulation in mammalian hibernation: enzyme and protein adaptations. 950 21

The mechanism of heat aggregation of proteins proposed by the author involves the stage of irreversible denaturation, the stage of nucleation, and the stage of growth of aggregates. It was shown that the initial parts of the kinetic curves of aggregation followed by monitoring the increase in absorbance (A) or intensity of light scattering (I) are linearized in coordinates (dA/dt; t) and (A; t2) (or, respectively, in coordinates (dI/dt; t) and (I; t2)). The slope of these linear anamorphoses is proportional to the product of the rate constant of irreversible denaturation and the rate constant of growth of aggregates. The mechanism of heat aggregation proposed is fulfilled for pig heart citrate synthase. The dI/dt versus t curves for heat aggregation of glycogen phosphorylase b from rabbit skeletal muscles display a lag period whose appearance is caused by intramolecular predenaturational changes in the enzyme molecule.
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PMID:Kinetics of heat aggregation of proteins. 952 33


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