Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.21 (CPT)
 4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human intestinal mucosa contains acyl-CoA:cholesterol acyltransferase activity. The enzyme has been studied by using oleylcarnitine, CoA and carnitine palmitoyltransferase as an oleyl-CoA regenerating system. The enzyme was found in the particulate fraction of the cells, it had a pH optimum between 7.2 and 8.2, and was inhibited by taurocholate. The specific enzymic activity in biopsies from intestinal mucosa of normal men was found to be 3.6 +/- 1.37 nmol cholesteryl ester formed mg protein-1 h-1, an activity which can account for all cholesteryl esters in intestinal lymph. Low enzymic activity was found in biopsies from patients with small intestinal disorders. Two pancreatectomized patients had values within the normal range.
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PMID:Esterification of cholesterol in human small intestine: the importance of acyl-CoA:cholesterol acyltransferase. 11 Jun 2

The study was designed to evaluate hepatic mitochondrial function during ketotic states. The ketogenic models studied were streptozotocin-induced diabetic ketoacidosis, 48 h of starvation, and after growth hormone administration. In the last-mentioned model we observed increased free fatty acids but not ketonemia. Oxidative phosphorylation was measured using the citric acid cycle substrates pyruvate and succinate, the amino acid glutamate, a ketone body beta-hydroxybutyrate, and a long-chain fatty acid palmitoyl-l-carnitine. State 3 (ADP stimulated) and state 4 (ADP limited) respiration, respiratory control ratio (state 3/state 4), and the ADP/O ratios were normal in the controls and the experimental groups. Uncoupled respiration produced by dinitrophenol with a variety of substrates was unchanged in the experimental groups compared to the controls. Fatty acid oxidation was studied in detail. The rate of utilization of palmitoyl-l-carnitine by controls or experimental groups did not depend on the product formed (citrate, acetoacetate). No significant changes were observed in the oxidation of palmitoyl-CoA (+ carnitine) or with an intermediate-chain fatty acid hexanoate. The specific activity of hepatic mitochondria carnitine palmitoyltransferase did not change in any of the three experimental groups. It is concluded that during diabetic ketoacidosis, starvation, and growth hormone administration, there is (a) no alteration in hepatic mitochondrial function; (b) no change in the intrinsic capacity of hepatic mitochondria to oxidize fatty acids; and (c) no change in the specific activity of mitochondrial carnitine palmitoyltransferase. The mechanism by which the body restrains flux through the mitochondrial oxidative machinery remains to be fully determined.
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PMID:Hepatic mitochondrial function in ketogenic states. Diabetes, starvation, and after growth hormone administration. 12 19

A 15-year-old girl with a large accumulation of lipid in the muscle fibers, was suffering from systemic carnitine deficiency. She died in acidosis. The blood carnitine level was normal. At necropsy, carnitine levels were low in skeletal muscles and heart, whilst a normal level was found in the liver. Carnitine palmitoyltransferase II and palmitoyl-CoA synthetase activities were increased, whereas carnitine acetyltransferase, glycerol-3-phosphate dehydrogenase (FAD) and succinate dehydrogenase were decreased. Investigation of blood and skeletal muscle of the family members revealed marked abnormalities in a 7-year old sister who had only minor neurological symptoms. Histochemical investigation revealed abnormal accumulations of lipid between the myofibrils. Carnitine was decreased in her skeletal muscle and blood. Muscular carnitine palmitoyltransferase II and palmitoyl-CoA synthetase were again increased in activity while glycerol-3-phosphate dehydrogenase (FAD) was decreased. The activities of succinate dehydrogenase, carnitine palmitoyltransferase I and glycerol-3-phosphate dehydrogenase (NAD+) were normal. The unexpected normal carnitine level in blood and liver of the deceased patient was attributed to muscle wasting, which was confirmed by the very high blood level of creatine phosphokinase. This fatal case indicates that the fasting condition must be avoided in persons with carnitine deficiency. In crises, glucose supply is necessary since gluconeogenesis may be blocked.
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PMID:Familial carnitine deficiency. A fatal case and subclinical state in a sister. 15 48

1. The acyl-CoA synthetase activity in brown adipose tissue of cold-exposed guinea pig has been studied by measuring the rate of palmitoylcarnitine formation in the presence of excess carnitine palmitoyltransferase. 2. The rate of palmitoylcarnitine formation in the mitochondria was found to be 161 plus or minus 64 nmol.mg-minus-1. min-minus-1 (n=9). 3. In the absence of added palmitate and bovine serum albumin a total of 35 plus or minus 1 nmol endogenous fatty acids.mg-minus-1 were activated with three different mitochondrial preparations. 4. Three different experimental approaches have been used to study the subcellular localization of the enzyme: (a) conventional differential centrifugation (De Duve, C., Pressman, B.C., Gianetto, R., Wattiaux, R. and Appelmans, F. (1955) Biochem. J. 60, 604-617) (B) the determination of the sediterm of different marker enzymes (Slinde, E. and Flatmark. T. (1973) Anal. Biochem. 56, 324-340) and (c) the determination of the stoichiometry between the activities of these enzymes sedimented at higher centrifugal effects. 5. Throughout all fractionation procedures, the long-chain acyl-CoA synthetase follows strictly the amine oxidase generally considered to be exclusively located on the mitochondrial outer membrane.
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PMID:The intracellular localization of long-chain acyl-CoA synthetase in brown adipose tissue. 16 54

The concentration of total carnitine (i.e. carnitine plus acetylcarnitine) was measured in seminal plasma and spermatozoa of men and rams. In ram semen, there was a close correlation between the concentration of spermatozoa and that of total carnitine in the seminal plasma, indicating that the epididymal secretion was the sole source of seminal carnitine. The percentage of total carnitine present as acetylcarnitine was 40% in seminal plasma and 70-80% in spermatozoa. The acetylation state of carnitine in seminal plasma was apparently not influenced by the metabolic activity of spermatozoa in ejaculated ram semen as no change was found in the plasma concentration of carnitine or acetylcarnitine up to 45 min after ejaculation. In spermatozoa, the activity of carnitine acetyltransferase (EC 2.3.1.7) was approximately equivalent to that of carnitine palmitoyltransferase (EC 2.3.1.21); and the activity of these enzymes was similar in ram and human spermatozoa but greater in rat spermatozoa. It is concluded that there is no correlation between the content of either total carnitine or the carnitine acyltransferases and the respiratory capacity of spermatozoa.
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PMID:Carnitine, acetylcarnitine and the activity of carnitine acyltransferases in seminal plasma and spermatozoa of men, rams and rats. 48 Mar 18

beta-Oxidation of long-chain fatty acids increases many-fold in atherosclerotic aortas; this may be due to an increase in the activity of the mitochondrial enzyme hexadecanoyl-CoA: carnitine O-hexadecanoyltransferase EC 2.3.1.23 (trivial name: carnitine palmitoyltransferase, CPT). To investigate this possibility, an assay for arterial CPT was developed and used to measure CPT activity in mitochondrial fractions isolated from aortas of rabbits fed high-fat (HF) or high-fat plus cholesterol (HFC) supplemented diets. The arterial CPT assay was linear with respect to mitochondrial protein between 0.03 and 0.30 mg and assay time between 3 and 12 min. Maximum CPT activity was observed at concentrations of palmitoyl-CoA between 5 and 25 micron, higher concentrations of palmitoyl-CoA inhibited CPT activity. CPT activity was measured in mitochondrial fractions isolated from aortas of rabbits fed the HFC-supplemented diet for up to 48 days. No visible lesions were observed in aortas of rabbits fed HFC-diet for 3,9, or 21 days, however, by 48 days atheromatous lesions covered in excess of 60% of the intimal surface of the aorta. No lesions were visually observed in aortas of rabbits receiving the HF-diet. Despite the development of gross atherosclerotic lesions, there were no changes in CPT activity observed that could account for a dramatic increase in fatty acid oxidation. It is concluded that the increase in beta-oxidation of long-chain fatty acids in atherosclerosis is not attributable to an increase in CPT activity.
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PMID:Carnitine palmitoyltransferase activity in mitochondrial fractions isolated from aortas of rabbits fed cholesterol-supplemented diets. 49 40

The assay conditions for palmitoyl-CoA synthetase (P-CoA S) and carnitine palmitoyltransferase (CPT) in homogenates of human blood platelets have been studied. The assay based on trapping of palmitoyl-CoA by carnitine in the presence of exogenous CPT gave higher activity of P-CoA S than the assay based on direct isolation of the palmitoyl-CoA formed. The activity of CPT was higher on exogenous palmitoyl-CoA than on endogenous palmitoyl-CoA formed from palmitic acid and CoA in the presence of endogenous P-CoA S. The activity of CPT was strongly dependent on the incubation time and the amount of platelets used. The initial activity of this enzyme in human blood platelets was higher than previously assumed.
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PMID:A study of assay conditions for palmitoyl-CoA synthetase and carnitine palmitoyltransferase in homogenates of human blood platelets. 52 50

1. Activities of 3-oxo acid CoA-transferase and carnitine palmitoyltransferase together with tri- and di-acylglycerol lipase were present in red and heart muscles of the teleost fish. However, d-3-hydroxybutyrate dehydrogenase activity was not detectable. These results suggest that the heart and red muscles of the teleosts should be able to utilize the fat fuels triacylglycerol, fatty acids or acetoacetate, but not hydroxybutyrate. The muscles from the elasmobranchs differed in that d-3-hydroxybutyrate dehydrogenase and 3-oxo acid CoA-transferase activities were present, but carnitine palmitoyltransferase activity was not detectable. This suggests that ketone bodies are the most important fat fuels in elasmobranchs. 2. The concentrations of acetoacetate, 3-hydroxybutyrate, glycerol, non-esterified fatty acids and triacylglycerols were measured in blood or plasma of several species of fish (teleosts and elasmobranchs) in the fed state. Teleosts have a 10-fold higher concentration of plasma non-esterified fatty acids, but a lower blood concentration of ketone bodies; both acetoacetate and 3-hydroxybutyrate are present in blood of elasmobranchs, whereas 3-hydroxybutyrate is absent from that of the teleosts. 3. The effects of starvation (up to 150 days) on the concentrations of blood metabolites were studied in a teleost (bass) and an elasmobranch (dogfish). In the bass there was a 60% decrease in blood glucose after 100 and 150 days starvation. In dogfish there was a large increase in the concentration of ketone bodies, whereas in bass the concentration of acetoacetate (the only ketone body present) remained low (<0.04mm) throughout the period of starvation. The concentration of plasma non-esterified fatty acids increased in bass, but decreased in dogfish. These changes are consistent with the predictions based on the enzyme-activity data. 4. Starvation did not change the activities of ketone-body-utilizing enzymes or that of phosphoenolpyruvate carboxykinase in heart and red skeletal muscles of both fish, but it decreased markedly the activity of phosphoenolpyruvate carboxykinase in white skeletal muscle of both fish. However, in the liver of the dogfish, starvation resulted in a twofold increase in the activities of 3-hydroxybutyrate dehydrogenase and acetoacetyl-CoA thiolase, whereas in bass liver it decreased the activity of acetoacetyl-CoA thiolase and increased that of 3-oxo acid CoA-transferase. The activity of phosphoenolpyruvate carboxykinase was increased twofold in the liver of bass, but was unchanged in that of the dogfish. 5. The difference in changes in concentrations of blood metabolites and enzyme activities in the two fish support the suggestion that, in starvation, ketone bodies, but not non-esterified fatty acids, are an important fuel for muscle in elasmobranchs, whereas non-esterified fatty acids, but not ketone bodies, are an important fuel in teleosts. The results are discussed in relation to the evolution of a discrete lipid-storing adipose tissue in teleosts and higher vertebrates.
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PMID:Activities of enzymes of fat and ketone-body metabolism and effects of starvation on blood concentrations of glucose and fat fuels in teleost and elasmobranch fish. 53 30

Buformin at a concentration of 1--2.5 mM stimulates solubilized carnitine palmitoyltransferase by reducing the inhibitory effect of palmitoyl-CoA. Neither buformin nor metformin inhibits the solubilized carnitine palmitoyltransferase.
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PMID:Effect of a biguanide (buformin) on carnitine palmitoyltransferase activity. 60 70

1. State-3 (i.e. ADP-stimulated) rates of O(2) uptake with palmitoylcarnitine, palmitoyl-CoA plus carnitine, pyruvate plus malonate plus carnitine and octanoate as respiratory substrate were all diminished in heart mitochondria isolated from senescent (24-month-old) rats compared with mitochondria from young adults (6 months old). By contrast, State-3 rates of O(2) uptake with pyruvate plus malate or glutamate plus malate were the same for mitochondria from each age group. 2. Measurements of enzyme activities in disrupted mitochondria showed a decline with senescence in the activity of acyl-CoA synthetase (EC 6.2.1.2 and 6.2.1.3), carnitine acetyltransferase (EC 2.3.1.7) and 3-hydroxy-acyl-CoA dehydrogenase (EC 1.1.1.35), but no change in the activity of carnitine palmitoyltransferase (EC 2.3.1.21) or acyl-CoA dehydrogenase (EC 1.3.99.3). 3. Measurement of dl-[(3)H]carnitine (in)/acetyl-l-carnitine (out) exchange in intact mitochondria showed decreased rates when the animals used were senescent. However, this followed from a decreased intramitochondrial pool of exchangeable carnitine, such that calculated first-order rate constants for exchange were identical in mitochondria from the two age groups. 4. The decline in acyl-CoA synthetase activity is thought to be the reason for the diminished rate of O(2) uptake with octanoate in senescence. The decline in carnitine acetyltransferase activity is considered to be the cause of the diminished rate of O(2) uptake with acetylcarnitine or with pyruvate plus malonate plus carnitine as substrate. The mechanism of the diminished rate of O(2) uptake with palmitoylcarnitine in senescence is discussed.
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PMID:Lipid oxidation by heart mitochondria from young adult and senescent rats. 63 43


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