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:2.3.1.21 (CPT)
4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carnitine acyltransferase activities in the hearts of normal and dystrophic, sedentary and swim exercised hamsters were studied, in order to analyze the relationship between carnitine metabolism and exercise in cardiomyopathy. After 12 weeks, the mean specific activities of cardiac carnitine acetyltransferase (CAT), carnitine octanoyltransferase (COT) and carnitine palmitoyltransferase (CPT) were significantly higher in the dystrophic sedentary group, relative to the normal sedentary group (p less than 0.05). There was no significant effect of exercise on the mean specific activity of the carnitine acyltransferases, compared to the dystrophic or normal sedentary controls. Thus, the improvements in cardiac histopathology due to exercise noted previously are not associated with altered carnitine acyltransferase activity.
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PMID:Cardiac carnitine acyltransferase activities in exercised normal and dystrophic hamsters. 178 40

Carnitine acyltransferase activities were studied in normal human skeletal muscle and in muscle of three patients with carnitine palmitoyltransferase deficiency. Carnitine acetyltransferase (CAT), carnitine octanoyltransferase (COT), and carnitine palmitoyltransferase (CPT) were differentiated (i) by the use of the substrates acetyl-CoA, octanoyl-CoA, lauroyl-CoA, and palmitoyl-CoA, (ii) by the inhibitors malonyl-CoA, chlorpromazine, and dithio-bis-nitrobenzoic acid (DTNB), and (iii) by the solubilities of the carnitine acyltransferase activities after centrifugation at 48,000 g for 30 min. The results are consistent with the notion of three different carnitine acyltransferases in human skeletal muscle: a membrane-bound malonyl-CoA-sensitive CPT, a soluble malonyl-CoA-insensitive CAT, and a malonyl-CoA-sensitive COT that is not attached to the mitochondrial membrane. The different solubilities of the carnitine acyltransferases allow a clear differentiation of CPT from CAT and COT in homogenates of previously frozen muscle biopsies whereas a separate determination of CAT and COT is only partially possible. In patients with CPT deficiency total CPT activity was within the normal range but was abnormally inhibited by malonyl-CoA and chlorpromazine. Activities of carnitine acyltransferases with the substrates acetyl-CoA and octanoyl-CoA were normal indicating that the biochemical defect in CPT deficiency is confined to CPT without compensatory changes of CAT and COT.
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PMID:Carnitine acyltransferases in normal human skeletal muscle and in muscle of patients with carnitine palmitoyltransferase deficiency. 182 3

The profile of the changes in the peroxisomal fatty acid oxidation activity in rat liver was compared with that in microsomal omega-oxidation under various conditions such as a 2-week administration of phenoxyacetic acid derivatives and perfluorinated compounds, short and long-term administration of clofibrate and bezafibrate, high-fat diet feeding, starvation and diabetes. The results were summarized as follows: 1) when phenoxyacetic acid derivatives and perfluorinated compounds were administered, there was a significant correlation in the increase of the activities between peroxisomal fatty acid oxidation and microsomal omega-oxidation. 2) On the long-term administration (79 weeks) of peroxisome proliferators the activities of the enzymes were significantly reduced, but the levels were still higher than the control level in a similar manner. 3) On high-fat diet feeding the patterns of the changes in the activities of peroxisomal fatty acid oxidation, carnitine acetyltransferase and microsomal omega-oxidation were similar to each other, differing from the changes in the activities of microsomal aminopyrin demethylase and mitochondrial carnitine palmitoyltransferase. 4) Under starved and diabetic conditions, co-induction of peroxisomal fatty acid oxidation and microsomal omega-oxidation was observed. From these results it is suggested that 1) the biosynthesis of these enzymes would be regulated on the gene expression of the nearby domain and 2) peroxisomal fatty acid oxidation and microsomal omega-oxidation were co-operatively regulated in order to achieve fatty acid metabolism smoothly.
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PMID:Characteristics of peroxisome proliferation: co-induction of peroxisomal fatty acid oxidation-related enzymes with microsomal laurate hydroxylase. 191 1

Salicylyl-CoA and benzoyl-CoA were good inhibitors of carnitine acetyltransferase (CAT), competing with acetyl-CoA with Ki values of 7.5 and 22 microM respectively in the forward direction and with CoA in the reverse reaction with similar Ki values. They were also competitive inhibitors of carnitine octanoyltransferase (Ki = 261 and 295 microM respectively), but were only weakly inhibitory to carnitine palmitoyltransferase. Inhibition of energy production by salicylate may result from the inhibition of CAT by salicylyl-CoA.
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PMID:Effect of carboxylic acid xenobiotics and their metabolites on the activity of carnitine acyltransferases. 195 85

In vivo administration of nicardipine, a known calcium antagonist, suppressed the clofibrate-evoked induction of activities of peroxisomal enzymes, such as catalase, the peroxisomal fatty acyl-CoA oxidizing system, carnitine acetyltransferase and mitochondrial carnitine palmitoyltransferase in rat liver. On a time-course study, the suppression of induction in the activities of the peroxisomal fatty acyl-CoA oxidizing system and carnitine acetyltransferase was found at 5 days after the treatment, whereas the induction by clofibrate was already observed at 1 day after the treatment, suggesting that in the process of peroxisome induction by clofibrate there might be two steps, i.e., a triggering step and an enhancing step, and nicardipine might act as suppressor for the later step. The precursor-incorporation studies with [3H]leucine showed that the rate of the synthesis of the peroxisomal bifunctional enzyme was increased by 4.2-fold after clofibrate-treatment, whereas nicardipine suppressed this enhancement to only 2.2-fold of the control. The rate of degradation of this enzyme was not affected by any treatment. These results show that nicardipine affects the regulation mechanism of the biosynthesis of this enzyme. Nicardipine showed hardly any suppressive-effect on the hepatic peroxisomal enzyme induction observed in high-fat diet fed rat. Furthermore, the suppression of clofibrate-evoked induction of peroxisomal enzymes was observed also in mice. These interesting findings suggest that there is a difference in the mechanism of peroxisome proliferation and/or the induction of peroxisomal enzymes between clofibrate and physiological conditions, such as high-fat diet feeding. The suppression of drug-induced peroxisome proliferation by calcium antagonists may help in dissecting the causal relationship between the multiple effects mediated by peroxisomal proliferators.
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PMID:Characteristics of the suppressive effect of nicardipine on peroxisome induction in rat liver. 229 37

The activities of palmitoyl-coenzyme A (CoA) synthetase, carnitine acetyltransferase (CAT), and carnitine palmitoyltransferase (CPT) and the levels of ketone bodies, reduced coenzyme A (CoASH), carnitine, and their esters, which are involved in fatty acid metabolism, in rat liver and plasma were measured after the administration of Escherichia coli lipopolysaccharide (LPS). We also studied the effect of L-carnitine treatment before LPS administration on survival and on hepatic fatty acid metabolism. The activities of CAT and CPT and the concentrations of ketone bodies, CoA, and carnitine derivatives (except for malonyl-CoA) declined in the liver after LPS administration. The activity of palmitoyl-CoA synthetase was changed little after LPS administration, and the level of hepatic malonyl-CoA increased significantly, suggesting that LPS causes activated fatty acids to undergo esterification and lipogenesis rather than oxidation. Treatment of rats with L-carnitine before LPS greatly increased the survival rate, but did not affect enzymes that metabolize fatty acids, CoA, or carnitine derivatives in the liver. Further studies are necessary to elucidate the mechanism of the effect of carnitine on post-LPS survival.
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PMID:Altered hepatic fatty acid metabolism in endotoxicosis: effect of L-carnitine on survival. 252 28

Clofibrate induces hypertrophy and hyperplasia and marked changes in the activities of various enzymes in rat liver. We examined the effects of treatment of rats with clofibrate on enzyme induction and on rates of metabolic flux in hepatocytes isolated from the periportal and perivenous zones of the liver. Clofibrate induced the activities of carnitine acetyltransferase (90-fold), carnitine palmitoyltransferase (3-fold) and NADP-linked malic enzyme (3-fold) to the same level in periportal as in perivenous hepatocytes, suggesting that these enzymes were induced uniformly throughout the liver acinus. Increased rates of palmitate metabolism and ketogenesis after clofibrate treatment were associated with: a more oxidised mitochondrial redox state; diminished responsiveness to glucagon and loss of periportal/perivenous zonation. Despite the marked liver enlargement and hyperplasia caused by clofibrate, the normal periportal/perivenous zonation of alanine aminotransferase and gluconeogenesis was preserved in livers of clofibrate-treated rats, indicating that clofibrate-induced hyperplasia does not disrupt the normal acinar zonation of these metabolic functions.
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PMID:Clofibrate induces carnitine acyltransferases in periportal and perivenous zones of rat liver and does not disturb the acinar zonation of gluconeogenesis. 277 85

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

A 7-year-old girl had external ophthalmoplegia, limb weakness, short stature, hearing loss, pigmentary degeneration of the retina, and increased CSF protein content. Muscle biopsy revealed vacuolar myopathy with accumulation of lipids. Electronmicroscopy showed abnormalities of shape, size, and internal structure of muscle mitochondria. Muscle activity of palmitoyl-CoA synthetase was decreased, and the content of lipids was increased. Serum and muscle carnitine levels were normal, as were muscle carnitine palmitoyltransferase and carnitine acetyltransferase.
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PMID:Lipid storage myopathy in Kearns-Sayre syndrome. 293 55

The direct effects of clofibrate analogues on carnitine acyltransferase activities and fatty acid metabolism were studied in cultured hepatocytes. Rat hepatocytes cultured with bezafibrate or ciprofibrate (0.1-10 micrograms/ml) for 48 h had increased activities of carnitine acetyltransferase (CAT; 4-6-fold) and carnitine palmitoyltransferase (CPT; 12-34%). The increase in CAT was higher in hepatocytes from the periportal zone (440%) of rat liver compared with cells from the perivenous zone (266%). In human hepatocytes, in contrast with rat, the fibrates did not cause a marked increase in CAT activity. The effects of fibrates on palmitate metabolism were dependent on the carnitine status. In the presence of exogenous carnitine (1 mM), rat hepatocytes cultured with bezafibrate had higher rates of total palmitate metabolism (29-34%) without increased partitioning of palmitate towards beta-oxidation, relative to control cultures. At low endogenous carnitine concentrations, cells cultured with bezafibrate had a greater increase in palmitate metabolism, esterification and cellular accumulation of triacylglycerol compared with the corresponding increases in the presence of carnitine. The changes in palmitate metabolism at either high or low carnitine concentrations were small in comparison with the changes in CAT activity. It is concluded that the increase in hepatic carnitine that occurs in vivo after fibrate feeding probably plays the major role in the changes in partitioning of fatty acid between beta-oxidation and esterification.
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PMID:Fatty acid metabolism in hepatocytes cultured with hypolipidaemic drugs. Role of carnitine. 304 53


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