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)

1. Deca-2,4,6,8-tetraenoic acid is a substrate for both ATP-specific (EC 6.2.1.2 or 3) and GTP-specific (EC 6.2.1.-) acyl-CoA synthetases of rat liver mitochondria. The enzymic synthesis of decatetraenoyl-CoA results in new spectral characteristics. The difference spectrum for the acyl-CoA minus free acid has a maximum at 376nm with epsilon(mM) 34. Isosbestic points are at 345nm and 440nm. 2. The acylation of CoA by decatetraenoate in mitochondrial suspensions can be continuously measured with a dual-wavelength spectrophotometer. 3. By using this technique, three distinct types of acyl-CoA synthetase activity were demonstrated in rat liver mitochondria. One of these utilized added CoA and ATP, required added Mg(2+) and corresponded to a previously described ;external' acyl-CoA synthetase. The other two acyl-CoA synthetase activities utilized intramitochondrial CoA and did not require added Mg(2+). Of these two ;internal' acyl-CoA synthetases, one was insensitive to uncoupling agents, was inhibited by phosphate or arsenate, and corresponded to the GTP-specific enzyme. The other corresponded to the ATP-specific enzyme. 4. Atractylate inhibited the activity of the two internal acyl-CoA synthetases only when the energy source was added ATP. 5. The amount of intramitochondrial CoA acylated by decatetraenoate was independent of whether the internal ATP-specific or GTP-specific acyl-CoA synthetase was active. It is concluded that these two internal acyl-CoA synthetases have access to the same intramitochondrial pool of CoA. 6. The amount of intramitochondrial CoA that could be acylated with decatetraenoate was decreased by the addition of palmitoyl-dl-carnitine, 2-oxoglutarate, or pyruvate. These observations indicated that pyruvate dehydrogenase (EC 1.2.4.1), oxoglutarate dehydrogenase (EC 1.2.4.2), carnitine palmitoyltransferase (EC 2.3.1.-), citrate synthase (EC 4.1.3.7), and succinyl-CoA synthetase (EC 6.2.1.4) all have access to the same intramitochondrial pool of CoA as do the two internal acyl-CoA synthetases.
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PMID:Spectrophotometric studies of acyl-coenzyme A synthetases of rat liver mitochondria. 550 Mar 16

Preflight development of the goslings was typified by rapid increases in the mitochondrial enzymes of the semimembranosus and heart ventricular muscles resulting in near-adult values by 3 wk of age. In contrast, aerobic capacity of the pectoralis muscle initially developed slowly but showed a rapid increase between 5 and 7 wk of age, in preparation for becoming airborne. Activities of glycolytic enzymes in the pectoralis muscle showed similar patterns of development as those found for the aerobic enzymes, except for hexokinase, which was low at all ages, indicating an adaptation for catabolism of both intracellular glycogen and plasma fatty acids in preference to plasma glucose. Muscle mass specific activity of citrate synthase in the pectoralis increased by only 33% from goslings during the first few days of flight, compared with premigratory geese. Activities of anaerobic glycolytic enzymes in the ventricles were low, but values for hexokinase, which is involved in the phosphorylation of plasma glucose, developed rapidly. Values for lactate dehydrogenase were also high, reflecting the capacity of the heart to catabolize plasma lactate. Substrate flux supplied by carnitine palmitoyltransferase and oxoglutarate dehydrogenase (OGD), in the pectoralis muscles of the premigratory geese, appears to have the smallest excess capacities to meet the requirements of sustained aerobic flight. The average maximum oxygen uptake for premigratory geese during flight, as indicated by values for OGD, is calculated to be 484 ml O2/min (or 208 ml O2.min-1.kg-1).
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PMID:Development of metabolic enzyme activity in locomotor and cardiac muscles of the migratory barnacle goose. 2679 34

Mitochondria were isolated from liver, heart and skeletal muscle of a 34-day-old female infant who died from a myopathic illness. Muscle biopsy showed lipid accumulation and no obvious pathology in any other organ. Enzymatic analysis of skeletal muscle extracts revealed normal activities of the markers pyruvate dehydrogenase and citrate synthase. Malonyl-CoA-sensitive carnitine palmitoyltransferase (CPT1) was detected but malonyl-CoA-insensitive carnitine palmitoyltransferase (CPT2) appeared to be absent. Quantitative immunoblotting revealed the presence of a normal abundance of CPT2 protein in the patient's muscle. It is concluded that enzymically inactive CPT2 protein was present.
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PMID:Neonatal carnitine palmitoyltransferase-2 deficiency: a case presenting with myopathy. 776 92

An understanding of the mechanism of malonyl-CoA interaction with carnitine palmitoyltransferase (CPT-I) in isolated mitochondria is complicated by membrane fragmentation and CPT-II exposure. Using cultured neonatal rat cardiac myocytes, as in situ model was developed to measure CPT-I. In the cardiac cells treated with 5 microM digitonin, CPT-II contamination of CPT activity is 0.62% as quantitated by citrate synthase activity present in damaged myocytes under assay conditions. Moreover, the sensitivity of myocyte CPT-I to malonyl-CoA, its substrate preference for decanoyl-CoA and the affinity of CPT-I for l-carnitine (0.19 mM) are comparable with similar measurements published for isolated cardiac mitochondrial membranes. There is no evidence in the cells for contamination of CPT-I activities by extramitochondrial sources, in particular, the sarcoplasmic reticulum (SR). The presence of carnitine octanoyltransferase (COT) is not detected either in the cells or in preparations of adult SR from which COT is subsequently isolated. With these control measurements, the inhibition kinetics of CPT-I in the cardiac cells in situ maintains a partial competitive pattern which is more pronounced with decanoyl-CoA than with palmitoyl-CoA as substrate. The presence of a malonyl-CoA/long chain acyl-CoA binding site on CPT-I, distinct from the inhibitory site, has previously been proposed. Existence of this binding region is consistent with partial inhibition kinetics so that malonyl-CoA at this site could modify the CPT-high-affinity malonyl-CoA inhibitory interaction, producing acylcarnitine even at high malonyl-CoA concentrations in the cell. These findings may help to explain, in part, the inability to suppress completely beta-oxidation in the heart where malonyl-CoA may be 50 to 100 times the estimated values of its Ki.
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PMID:Kinetic properties of carnitine palmitoyltransferase I in cultured neonatal rat cardiac myocytes. 791 95

Rat carnitine palmitoyltransferase (CPT) II was expressed in Saccharomyces cerevisiae. Mitochondrial fractions prepared from the cells displayed high CPT activity and reacted with an antibody to the rat protein on immunoblots, whereas no activity or immunoreactive protein was observed in control cells. The recombinant enzyme was largely membrane associated. Treatment of the expressed protein with diethyl pyrocarbonate, a reagent that modifies histidine residues, abolished CPT activity, but this was completely restored by reversal of the modification with hydroxylamine. It is inferred that a histidine residue plays a critical role in CPT function. Expression and analysis of site-directed mutants of CPT II showed that histidine 372, as well as aspartates 376 and 464 (all conserved throughout the carnitine/choline acyltransferase family), are essential for catalytic activity. The data suggest that the mechanism by which CPT II effects transesterification between palmitoyl-CoA and carnitine possibly involves histidine 372 and one of these aspartate residues, interacting with the carnitine hydroxyl group, in a reaction analogous to that carried out by a histidine/aspartate/serine catalytic triad in certain other enzyme systems. Mutagenic analysis of a region of CPT II that is highly conserved among the carnitine and choline acyltransferases, and which is homologous to the "adenine binding loop" of citrate synthase, implies that it has no similar function in CPT II.
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PMID:Catalytically important domains of rat carnitine palmitoyltransferase II as determined by site-directed mutagenesis and chemical modification. Evidence for a critical histidine residue. 803 73

1. Viable myocytes were obtained from rat hearts. Oxidation of [1-14C]palmitate by these cells could be decreased by the addition of glucose (5 mM) or lactate (2 mM). In the presence of glucose, insulin decreased and adrenaline increased palmitate oxidation. 2. The myocytes contained activities of ATP citrate-lyase, acetyl-CoA carboxylase and the condensing enzyme of the fatty acid elongation system. No fatty acid synthase activity was demonstrable in myocytes. 3. In rat hearts perfused with 5 mM glucose, malonyl-CoA content was acutely raised by insulin. In the presence of glucose+insulin, perfusion with palmitate or adrenaline decreased the malonyl-CoA content. 4. It is concluded that malonyl-CoA can be synthesized within cardiac myocytes and that the level of this metabolite can be acutely regulated. This is likely to have consequences for the regulation of carnitine palmitoyltransferase in the heart.
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PMID:Malonyl-CoA metabolism in cardiac myocytes and its relevance to the control of fatty acid oxidation. 821 40

We examined effects of temperature acclimation on ultrastructural characteristics of cardiac myocytes and maximal activities of metabolic enzymes in cardiac tissue of striped bass (Morone saxatilis). Ventricular mass and ventricular mass divided by body weight were significantly increased (29% and 40%, respectively) in animals acclimated to cold (5 degrees C) vs. warm temperatures (25 degrees C). Mean myocyte diameter was increased at cold temperature (3.47 +/- 0.14 vs. 2.98 +/- 0.08 microns), which is sufficient to explain the increase in ventricular mass. Ventricular enlargement did not alter volume densities of mitochondria, myofibrils, protein concentration, or citrate synthase activity. Thus total volume of mitochondria and myofibrils increased proportionately with cardiac mass in cold animals. Activities of hexokinase (34%) and carnitine palmitoyltransferase (42%) increased in cold animals, suggesting positive compensation and increased aerobic capacity for utilization of glucose and fatty acids for energy production. Enlargement of the ventricle and an increased capacity for ATP production in striped bass may help compensate for kinetic constraints at cold temperatures and maintain circulatory support to oxidative axial musculature for swimming activity.
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PMID:Structural and biochemical analyses of cardiac ventricular enlargement in cold-acclimated striped bass. 924 57

Carnitine palmitoyltransferase II (CPT II) deficiency is the most common lipid myopathy in adults and is characterized by exercise-induced pain, stiffness, and myoglobinuria. Retrospective analysis of patients with CPT II deficiency has made it possible to correlate the presence of disease-causing mutations in the CPT2 gene with residual CPT activity in muscle. We present evidence that the ratio of CPT II activity to citrate synthase activity in the skeletal muscle of patients presumed to have CPT II deficiency is important for predicting whether the patient has one, two, or no mutations in the CPT2 gene. This finding will assist in the future correlation of the phenotype with the genotype and in identifying manifesting heterozygotes.
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PMID:Biochemical and molecular correlations in carnitine palmitoyltransferase II deficiency. 1039 18

3-Thia fatty acids are potent hypolipidemic fatty acid derivatives and mitochondrion and peroxisome proliferators. Administration of 3-thia fatty acids to rats was followed by significantly increased levels of plasma ketone bodies, whereas the levels of plasma non-esterified fatty acids decreased. The hepatic mRNA levels of fatty acid binding protein and formation of acid-soluble products, using both palmitoyl-CoA and palmitoyl-L-carnitine as substrates, were increased. Hepatic mitochondrial carnitine palmitoyltransferase (CPT) -II and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase activities, immunodetectable proteins, and mRNA levels increased in parallel. In contrast, the mitochondrial CPT-I mRNA levels were unchanged and CPT-I enzyme activity was slightly reduced in the liver. The CoA ester of the monocarboxylic 3-thia fatty acid, tetradecylthioacetic acid, which accumulates in the liver after administration, inhibited the CPT-I activity in vitro, but not that of CPT-II. Acetoacetyl-CoA thiolase and HMG-CoA lyase activities involved in ketogenesis were increased, whereas the citrate synthase activity was decreased. The present data suggest that 3-thia fatty acids increase both the transport of fatty acids into the mitochondria and the capacity of the beta-oxidation process. Under these conditions, the regulation of ketogenesis may be shifted to step(s) beyond CPT-I. This opens the possibility that mitochondrial HMG-CoA synthase and CPT-II retain some control of ketone body formation.
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PMID:Mitochondrial 3-hydroxy-3-methylglutaryl coenzyme A synthase and carnitine palmitoyltransferase II as potential control sites for ketogenesis during mitochondrion and peroxisome proliferation. 1079 71

Selective breeding is an important tool in behavioral genetics and evolutionary physiology, but it has rarely been applied to the study of exercise physiology. We are using artificial selection for increased wheel-running behavior to study the correlated evolution of locomotor activity and physiological determinants of exercise capacity in house mice. We studied enzyme activities and their response to voluntary wheel running in mixed hindlimb muscles of mice from generation 14, at which time individuals from selected lines ran more than twice as many revolutions per day as those from control (unselected) lines. Beginning at weaning and for 8 wk, we housed mice from each of four replicate selected lines and four replicate control lines with access to wheels that were free to rotate (wheel-access group) or locked (sedentary group). Among sedentary animals, mice from selected lines did not exhibit a general increase in aerobic capacities: no mitochondrial [except pyruvate dehydrogenase (PDH)] or glycolytic enzyme activity was significantly (P < 0.05) higher than in control mice. Sedentary mice from the selected lines exhibited a trend for higher muscle aerobic capacities, as indicated by higher levels of mitochondrial (cytochrome-c oxidase, carnitine palmitoyltransferase, citrate synthase, and PDH) and glycolytic (hexokinase and phosphofructokinase) enzymes, with concomitant lower anaerobic capacities, as indicated by lactate dehydrogenase (especially in male mice). Consistent with previous studies of endurance training in rats via voluntary wheel running or forced treadmill exercise, cytochrome-c oxidase, citrate synthase, and carnitine palmitoyltransferase activity increased in the wheel-access groups for both genders; hexokinase also increased in both genders. Some enzymes showed gender-specific responses: PDH and lactate dehydrogenase increased in wheel-access male but not female mice, and glycogen phosphorylase decreased in female but not in male mice. Two-way analysis of covariance revealed significant interactions between line type and activity group; for several enzymes, activities showed greater changes in mice from selected lines, presumably because such mice ran more revolutions per day and at greater velocities. Thus genetic selection for increased voluntary wheel running did not reduce the capability of muscle aerobic capacity to respond to training.
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PMID:Effects of voluntary activity and genetic selection on muscle metabolic capacities in house mice Mus domesticus. 1100 2


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