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)

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 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

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.
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PMID:The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm. 439 82

The activities of five enzymes involved in acetyl-CoA synthesis, pyruvate dehydrogenase complex, ATP citrate lyase, carnitine acetyltransferase, acetyl-CoA synthetase, and citrate synthase, were determined in normal nucleus interpeduncularis and nucleus interpeduncularis in which cholinergic terminals were removed following lesion of the habenulointerpeduncular tract. The activities of aspartate transaminase, fumarase, and GABA transaminase also were determined to compare the effect of lesion on other mitochondrial enzymes which are not linked to the biosynthesis of ACh. In normal nucleus interpeduncularis the activities of carnitine acetyltransferase and pyruvate dehydrogenase complex were higher than the activity of ChAT (choline acetyltransferase), whereas the activities of acetyl-CoA synthetase and citrate synthase were considerably lower than that of ChAT. The effect of the lesion separated the enzymes into two groups: the activities of pyruvate dehydrogenase complex, carnitine acetyltransferase, fumarase and aspartate transaminase decreased by 30--40%, whereas the activities of the other enzymes descreased 5--15%. ChAT activity was in all cases less than 15% of normal. It could be concluded that none of the acetyl-CoA synthesizing enzymes decreased to the degree that ChAT did. Only pyruvate dehydrogenase complex and carnitine acetyltransferase seem to be localized in cholinergic terminals to a significant degree. ATP citrate lyase as well as acetyl-CoA synthetase seem to have less significance in supporting acetyl-CoA formation in cholinergic nerve terminals.
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PMID:Acetyl-CoA synthesizing enzymes in cholinergic nerve terminals. 610 88

The activities of ATP-citrate lyase in frog, guinea pig, mouse, rat, and human brain vary from 18 to 30 mu mol/h/g of tissue, being several times higher than choline acetyltransferase activity. Activities of pyruvate dehydrogenase and acetyl coenzyme A synthetase in rat brain are 206 and 18.4 mu mol/h/g of tissue, respectively. Over 70% of the activities of both choline acetyltransferase and ATP-citrate lyase in secondary fractions are found in synaptosomes. Their preferential localization in synaptosomes and synaptoplasm is supported by RSA values above 2. Acetyl CoA synthetase activity is located mainly in whole brain mitochondria (RSA, 2.33) and its activity in synaptoplasm is low (RSA, 0.25). The activities of pyruvate dehydrogenase, citrate synthase, and carnitine acetyltransferase are present mainly in fractions C and Bp. No pyruvate dehydrogenase activity is found in synaptoplasm. Striatum, cerebral cortex, and cerebellum contain similar activities of pyruvate dehydrogenase, citrate synthase, carnitine acetyltransferase, fatty acid synthetase, and acetyl-CoA hydrolase. Activities of acetyl CoA synthetase, choline acetyltransferase and ATP-citrate lyase in cerebellum are about 10 and 4 times lower, respectively, than in other parts of the brain. These data indicate preferential localization of ATP-citrate lyase in cholinergic nerve endings, and indicate that this enzyme is not a rate limiting step in the synthesis of the acetyl moiety of ACh in brain.
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PMID:Regional and subcellular distribution of ATP-citrate lyase and other enzymes of acetyl-CoA metabolism in rat brain. 610 1


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