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)

Male 13-lined ground squirrels induced to emerge from hibernation resumed feeding and gained weight. The weight gain was supported by increases in the levels of glucose 6-phosphate dehydrogenase, L-alanine aminotransferase and carnitine acetyltransferase in the liver. Maturation of the testis occurred in a period of about 16 days spanning the time of induced arousal. The testes of hibernating males were characterized by higher levels of L-alanine aminotransferase, glucose 6-phosphate dehydrogenase and 3-hydroxyacyl-CoA dehydrogenase than the testes of aroused males. Hexokinase, carnitine acetyltransferase and citrate synthase levels were similar in the testes of hibernating and aroused males. 3-Hydroxyacyl-CoA dehydrogenase was more active and L-alanine aminotransferase less active in ground squirrel sperm than in rat sperm.
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PMID:Changes in enzyme levels in the testis and liver of the 13-lined ground squirrel (spermophilus tridecemlineatus) at the time of arousal from hibernation. 7 Oct 81

1. Enzyme activities (units/g wet wt.) were determined in the caput and cauda epididymidis and in epididymal spermatozoa of the rat. 2. The activity of most enzymes in the cauda was between 50 and 100% of that in the caput, except that ATP citrate lyase was barely detectable in the cauda. 3. Spermatozoa, unlike epididymal tissue, contained sorbitol dehydrogenase but lacked ATP citrate lyase. NADP+-malate dehydrogenase, mitochondrial glycerol 3-phosphate dehydrogenase, succinate dehydrogenase, carnitine acetyltransferase and citrate synthase were 5 to 400 times as active in spermatozoa as in epididymal tissue. 4. 2-Oxoglutarate dehydrogenase was the least active member of the tricarboxylic acid cycle in all tissues and most closely matched the measured flux through the cycle. 5. The concentrations of hydroxyacyl-CoA dehydrogenase and carnitine palmitoyltransferase were equivalent to the more active enzymes of the tricarboxylic acid cycle, indicating the capacity for extensive lipid oxidation, and the presence of 3-hydroxybutyrate dehydrogenase suggests that these tissues can also oxidize ketone bodies. 6. Transfer of reducing equivalents from cytoplasm to mitochondrion is unlikely to occur by means of the glycerol phosphate cycle because mitochondrial glycerol 3-phosphate dehydrogenase is relatively inactive in epididymal tissue, whereas the cytoplasmic enzyme has little activity in spermatozoa, but transfer may be accomplished by the malate-aspartate shuttle. 7. Transfer of acetyl units from mitochondrion to cytoplasm could be effected by the pyruvate-malate cycle in the caput of androgen-maintained rats, but not in the other tissues because of the low activity of ATP citrate lyase. Acetyl unit transfer could take place via acetylcarnitine, mediated by carnitine acetyltransferase. 8. Castration resulted in a decrease in the concentration of nearly all enzymes, although subsequent administration of testosterone restored concentrations to values similar to those in animals maintained by endogenous androgen. The extent to which enzyme concentration was changed by an alteration in androgen status was highly variable, but was most marked in the case of pyruvate carboxylase.
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PMID:Activity and androgenic control of enzymes associated with the tricarboxylic acid cycle, lipid oxidation and mitochondrial shuttles in the epididymis and epididymal spermatozoa of the rat. 72 83

Carnitine acetyltransferase was isolated from yeast Saccharomyces cerevisiae with an apparent molecular weight of 400,000. The enzyme contains identical subunits of 65,000 Da. The Km values of the isolated enzyme for acetyl-CoA and for carnitine were 17.7 microM and 180 microM, respectively. Carnitine acetyltransferase is an inducible enzyme, a 15-fold increase in the enzyme activity was found when the cells were grown on glycerol instead of glucose. Carnitine acetyltransferase, similarly to citrate synthase, has a double localization (approx. 80% of the enzyme is mitochondrial), while acetyl-CoA synthetase was found only in the cytosol. In the mitochondria carnitine acetyltransferase is located in the matrix space. The incorporation of 14C into CO2 and in lipids showed a similar ratio, 2.9 and 2.6, when the substrate was [1-14C]acetate and [1-14C]acetylcarnitine, respectively. Based on these results carnitine acetyltransferase can be considered as an enzyme necessary for acetate metabolism by transporting the activated acetyl group from the cytosol into the mitochondrial matrix.
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PMID:Isolation and characterization of carnitine acetyltransferase from S. cerevisiae. 189 91

Glycolyl-CoA can be formed during the course of the beta-oxidation by rat liver mitochondria of 4-hydroxybutyrate. The existence of this beta-oxidation has been previously supported by the occurrence of 4-hydroxybutyrate and its beta-oxidation catabolites in urine from patients with 4-hydroxybutyric aciduria, an inborn error of gamma-aminobutyric acid metabolism due to the deficiency of succinic semialdehyde dehydrogenase. The characteristics of the mitochondrial beta-oxidation of 4-hydroxybutyrate were, in rat liver, compared with those of the mitochondrial beta-oxidation of butyrate. The inhibition by malonate of the oxidation of 4-hydroxybutyrate was about twofold weaker than that of oxidation of butyrate, whereas both oxidations were abolished by preincubating the mitochondria with 1 mM valproic acid, a known inhibitor of mitochondrial beta-oxidation. Mitochondria from rat kidney cortex were demonstrated to catalyse, as previously shown for hepatic mitochondria, the carnitine-dependent oxidation of 12-hydroxylauroyl-CoA-omega-Hydroxymonocarboxylyl-CoAs are thus concluded to be precursors of glycolyl-CoA also in rat kidney cortex. In addition, 3-hydroxypyruvate was found to be a precursor of glycolyl-CoA, since it was oxidized by bovine heart pyruvate dehydrogenase with a cofactor requirement similar to that of pyruvate oxidation. Glycolyl-CoA was a substrate of carnitine acetyltransferase (pigeon breast muscle). Pig heart citrate synthase was capable of catalyzing the condensation of glycolyl-CoA with oxaloacetate. The product of this reaction induced low NADH production rates dependent on the addition of porcine heart aconitase and isocitrate dehydrogenase.
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PMID:Studies on the metabolism of glycolyl-CoA. 197 13

Radioisotopic assays for the determination of acetyl-CoA, CoASH, and acetylcarnitine have been modified for application to the amount of human muscle tissue that can be obtained by needle biopsy. In the last step common to all three methods, acetyl-CoA is condensed with [14C]oxaloacetate by citrate synthase to give [14C]-citrate. For determination of CoASH, CoASH is reacted with acetylphosphate in a reaction catalyzed by phosphotransacetylase to yield acetyl-CoA. In the assay for acetylcarnitine, acetylcarnitine is reacted with CoASH in a reaction catalyzed by carnitine acetyltransferase to form acetyl-CoA. Inclusion of new simple steps in the acetylcarnitine assay and conditions affecting the reliability of all three methods are also described. Acetylcarnitine and free carnitine levels in human rectus abdominis muscle were 3.0 +/- 1.5 (SD) and 13.5 +/- 4.0 mumol/g dry wt, respectively. Values for acetyl-CoA and CoASH were about 500-fold lower, 6.7 +/- 1.8 and 21 +/- 8.9 nmol/g dry wt, respectively. A strong correlation between acetylcarnitine (y) and short-chain acylcarnitine (x), determined as the difference between total and free carnitine, was found in biopsies from the vastus lateralis muscle obtained during intense muscular effort, y = 1.0x + 0.5; r = 0.976.
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PMID:Radioisotopic assays of CoASH and carnitine and their acetylated forms in human skeletal muscle. 233 83

The rate of utilization of pyruvate (at various concentrations) was measured in lymphocytes prepared from rat mesenteric lymph nodes. The quantitative contribution of pyruvate to CO2, lactate, aspartate, alanine, citrate, acetate, acetyl-CoA and ketone bodies accounted for the pyruvate metabolized. Pyruvate utilization was depressed by increasing concentrations of pyruvate. The maximum catalytic activities and selected intracellular distributions of the following enzymes of pyruvate, citrate and acetyl-CoA metabolism were measured: citrate synthase, ATP-citrate lyase, lactate dehydrogenase, acetyl-CoA hydrolase, acetylcarnitine transferase, NAD+- and NADP+- isocitrate dehydrogenases, HMG-CoA lyase, HMG-CoA synthase, Pyruvate dehydrogenase, acetoacetyl-CoA thiolase, 3-oxoacid-CoA transferase, 3-hydroxybutyrate dehydrogenase and pyruvate carboxylase. Acetyl-CoA formed from pyruvate did not contribute to the respiratory energy metabolism of resting lymphocytes. Instead acetyl-CoA was converted to acetoacetate by reactions which may favour the pathway catalyzed by acetoacetyl-CoA thiolase and 3-oxoacid-CoA transferase. Acetate, acetyl- and palmitoyl-carnitine inhibited the decarboxylation of [1-14C] pyruvate. These observations may be connected with the suppression of pyruvate utilization by increased pyruvate substrate concentration. Only very small amounts of either pyruvate or acetate were incorporated into lipids in resting lymphocytes. The amounts incorporated were partitioned in approximately the same pattern into FFA, T.G., cholesterol and cholesterol esters. Taken together the data show that pyruvate metabolism is directed inter alia at the formation of acetoacetate which may serve as a lipid synthesis precursor. When pyruvate utilization and metabolism was enhanced by concanavalin A, then acetoacetate formation was not favoured and from this it is proposed that the acetyl units may then be directed into lipid synthesis and may also make a contribution to the energy metabolism of the activated lymphocyte.
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PMID:Pyruvate metabolism by lymphocytes: evidence for an additional ketogenic tissue. 261 47

The activities of carnitine acyltransferases and acyl-CoA hydrolases were determined in human and rat liver to establish the validity of extrapolating from studies on rats to human metabolism. In human liver, carnitine acetyltransferase activity was 10-14 times higher and carnitine octanoyltransferase 1.7-2.4 times higher than in rat liver, while carnitine palmitoyltransferase activity was similar in human and rat. Acetyl-CoA hydrolase and octanoyl-CoA hydrolase activities were lower in human (42-57%) than in rat liver, but palmitoyl-CoA hydrolase activity was similar in both species. The activity of citrate synthase was lower (44%) in human than in rat liver. The low citrate synthase activity and the high carnitine acetyltransferase in human liver suggest that in man acetylcarnitine might be more important as a vehicle for export of acetyl units from mitochondria than citrate. The high activity of carnitine acetyltransferase in human liver is consistent with the observation that acetylcarnitine is the predominant acylcarnitine excreted in diabetic ketosis in man. It is concluded that the rat may not be a valid model for carnitine metabolism in man, and that in human liver carnitine may have an important role in transfer of acetyl groups out of mitochondria and possibly also to extra-hepatic tissues.
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PMID:Carnitine acyltransferases and acyl-CoA hydrolases in human and rat liver. 288 46

Experimental hyperthyroidism induced in rats by daily injections of 3,3',5,5'-tetraiode-L-thyroxine (0.5 mg/kg i.p.) for 14 days resulted in a significant increase in heart weight and heart weight/body weight ratio. Hemodynamic and morphological studies were performed in one group. Thyroxine-treated rats showed a characteristic cardiovascular hyperdynamic state, such as tachycardia and augmented rate of contraction, but no evidence of heart failure such as elevated end-diastolic pressures. The cardiac cells in hyperthyroid rats had a significantly larger diameter and more mitochondria than did those of the control rats. In another group the activities of cardiac enzymes involved in energy utilization and liberation were measured biochemically and compared with those of normal controls. Hyperthyroidism resulted in increased specific activity of cytochrome C oxidase and actomyosin ATPase in the myocardium. The specific activity of long-chain acyl-CoA synthetase, carnitine palmityl-transferase, carnitine acetyltransferase, malate dehydrogenase and citrate synthase showed a moderate to marked increment, whereas the specific activity of lactate dehydrogenase and pyruvate kinase remained at the control values. These results suggest that in hyperthyroid rat hearts the functions of both energy liberation and utilization systems are enhanced to meet the added workload. Moreover, the increased activity of the enzymes participating in fatty acid metabolism suggest that in thyroxine-induced hypertrophic and hyperdynamic rat hearts, fatty acids contribute more to the energy supply than do carbohydrates.
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PMID:Biochemical and morphological study of cardiac hypertrophy. Effects of thyroxine on enzyme activities in the rat myocardium. 315 81

The activities of certain key enzymes have been measured in the ventral medial and ventral lateral areas of the hypothalamus, which are implicated in feeding behaviour, and compared with enzyme activities in the cortex and brainstem. The enzymes measured are concerned with glucose metabolism [hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49)], ketone body metabolism [3-hydroxybutyrate dehydrogenase (EC 1.1.1.30)], fatty acid utilisation [carnitine palmitoyl transferase (EC 2.3.1.7)], citric acid cycle activity [pyruvate dehydrogenase (EC 1.2.4.2) and citrate synthase (EC 4.1.3.7)] and neurotransmitter synthesis [glutamate dehydrogenase (EC 1.4.1.3)].
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PMID:Enzyme activities in regions of the hypothalamus. 380 3

Modifications of enzyme activities (creatine kinase and its B subunit; adenylate kinase; hexokinase; phosphofructokinase; lactate dehydrogenase; malate dehydrogenase, isocitrate dehydrogenase; citrate synthase; acetylcarnitine transferase; beta-hydroxyacetyl-CoA dehydrogenase; cytochrome c oxidase) in gastrocnemius muscle and myocardium were reported after two forms of training with or without administration of anabolic steroid. Endurance training was on a horizontal motor-driven treadmill, 2 km X hr-1, 5 days a week for 0.5 hr per day for 5 weeks. In the case of power endurance training there was a slope of 45 degrees. Enzyme activities in controls and treated guinea pigs, as well as treatment-induced enzyme activity changes are time dependent. Some of these activities correlate linearly with one another; such correlations characterize the effect of adaptation. Endurance training and power endurance training in this study induce similar modifications and seem to differ essentially in the daily work load. The anabolic steroid methandrostenolone (dianabol) induces modifications which training does not bring about but which training at least partially eliminates.
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PMID:Effects of training and methandrostenolone (an anabolic steroid) on energy metabolism in the guinea pig: changes in enzyme activities in gastrocnemius muscle and myocardium. 407 21


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