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)

The activities of carnitine octanoyltransferase (COT) and carnitine palmitoyltransferase (CPT) in rat liver were markedly increased by administration of di(2-ethyl-hexyl)phthalate. COT and CPT were purified from the enzyme-induced rat liver. COT was a 66,000-dalton polypeptide. The molecular weight of native CPT was 280,000--320,000 daltons, and the enzyme consisted of 69,200-dalton polypeptides. CAT, COT, and CPT were immunologically different. COT exhibited activity with all of the substrates tested (acyl-CoA's and acylcarnitines of saturated fatty acids having carbon chain lengths of C2--C20), though maximum activity was observed with hexanoyl derivatives. CPT exhibited catalytic activity with medium- and long-chain acyl derivatives. 2-Bromo-palmitoyl-CoA inactivated COT but not CPT. Malonyl-CoA inhibited CPT but not COT. CPT was confined to mitochondria, whereas COT was found in peroxisomes and the soluble compartment but not in mitochondria.
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PMID:Purification and properties of carnitine octanoyltransferase and carnitine palmitoyltransferase from rat liver. 663 Jan 73

Carnitine octanoyltransferase (COT) purified from rat liver microsomes has K0.5 values between 1.0 and 4.0 microM for saturated 6-carbon to 16-carbon length acyl-CoAs, with little differences in Vmax values. The reaction rate is linear with time in the forward direction (acyl-CoA-->acylcarnitine), but it increases with time when assayed in the reverse direction (acylcarnitine-->acyl-CoA). The K0.5 for decanoylcarnitine and CoASH are 0.3 mM for CoASH and between 1.0 and 4.0 mM for decanoylcarnitine. The kinetic data indicate that the enzyme functions in the direction of acyl-carnitine formation. It is moderately inhibited by aminocarnitine, and D-carnitine and etomoxiryl-CoA are weak inhibitors; malonyl-CoA does not inhibit the enzyme. The enzyme has little, if any, capacity to use valproylcarnitine, 3-methylglutarylcarnitine, or pivaloylcarnitine as a substrate. Polyclonal antibodies prepared against COT give a positive Western blot against the purified enzyme and against a protein in microsomes having the molecular mass of COT (53 kDA). Antimitochondrial CPT and antiperoxisomal CAT did not show appreciable cross-reactivity with purified microsomal COT. The inhibitor data, the kinetic data, the molecular masses, and the Western blotting profiles all show that the enzyme purified from rat liver microsomes is a different carnitine acyltransferase than those previously purified from other organelles.
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PMID:Properties of the medium chain/long chain carnitine acyltransferase purified from rat liver microsomes. 844 Jul 34

The subcellular site of oxidation of [1-14C]phytanic acid to pristanic acid and CO2 was examined by measurement of the release of 14CO2 in different organelles from human and rat tissues prepared by isopycnic density gradient centrifugation in Nycodenz. The activity of phytanic acid oxidation in human tissues (liver and cultured skin fibroblasts) paralleled that of the peroxisomal marker catalase. We also observed that Nycodenz (commonly used gradient material for isolation of subcellular organelles) has a strong inhibitory effect on the alpha-oxidation of phytanic acid. This inhibition is reversible and can be decreased or eliminated by dialysis of isolated organelles against isotonic solution. The dialysis of endoplasmic reticulum, mitochondrial, and peroxisomal fractions from human liver and cultured skin fibroblasts for 2 h against isotonic solution increased the specific activity of phytanic acid oxidation by 1.3-, 1.3-, and 5-21-fold, respectively, after removal of Nycodenz as compared with nondialyzed samples. After dialysis, the rate of oxidation of phytanic acid in peroxisomes from human liver and cultured skin fibroblasts was 4-26 times higher than that in mitochondria and 43-130 times than that in the endoplasmic reticulum, suggesting that, in human tissues, phytanic acid is oxidized to pristanic acid in peroxisomes. On the other hand, the oxidation of phytanic acid in rat liver paralleled the distribution of the mitochondrial marker cytochrome-c oxidase. The 18-fold higher rate of oxidation in dialyzed mitochondria (198.6 +/- 4.20 pmol/h/mg of protein) than in peroxisomes (11.0 +/- 0.5 pmol/h/mg of protein) demonstrates that, in rodents, phytanic acid is oxidized in mitochondria. 2-[5-(4-Chlorophenyl)pentyl]oxiran-2-carboxylic acid, an inhibitor of carnitine palmitoyltransferase I and mitochondrial fatty acid oxidation, inhibits the oxidation of phytanic acid in rat tissues (liver and cultured skin fibroblasts), whereas it has no effect on the oxidation of phytanic acid in human tissues (liver and cultured skin fibroblasts). The higher specific activity of phytanic acid oxidation in peroxisomes compared with that in mitochondria and the endoplasmic reticulum from human tissues and the inhibition of phytanic acid oxidation by 2-[5-(4-chlorophenyl)pentyl]oxiran-2-carboxylic acid in rat tissues (but not human tissues) demonstrate clearly that, in human tissues, phytanic acid is predominantly oxidized in peroxisomes.
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PMID:Phytanic acid alpha-oxidation. Differential subcellular localization in rat and human tissues and its inhibition by nycodenz. 848 24

The expression of several genes involved in intra- and extracellular lipid metabolism, notably those involved in peroxisomal and mitochondrial beta-oxidation, is mediated by ligand-activated receptors, collectively referred to as peroxisome proliferator-activated receptors (PPARs). To gain more insight into the control of expression of carnitine palmitoyltransferase (CPT) genes, which are regulated by fatty acids, we have examined the transcriptional regulation of the human MCPT I gene. We have cloned by polymerase chain reaction the 5'-flanking region of this gene and demonstrated its transcriptional activity by transfection experiments with the CAT gene as a reporter. We have also shown that this is a target gene for the action of PPARs, and we have localized a PPAR responsive element upstream of the first exon. These results show that PPAR regulates the entry of fatty acids into the mitochondria, which is a crucial step in their metabolism, especially in tissues like heart, skeletal muscle and brown adipose tissue in which fatty acids are a major source of energy.
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PMID:Control of human muscle-type carnitine palmitoyltransferase I gene transcription by peroxisome proliferator-activated receptor. 953 28

Insulin has been known to regulate intracellular metabolism by modifying the activity or location of many enzymes but it is only in the past few years that the regulation of gene expression is recognized to be a major action of this hormone. The present work provides evidences that insulin inhibits delta-aminolevulinate synthase (ALA-S) gene expression, the enzyme which governs the rate-limiting step in heme biosynthesis. The addition of 5 nM insulin to hepatocytes culture led to a significant decrease of both basal and phenobarbital-induced ALA-S mRNA in a dose-dependent manner, as measured by Northern and slot-blot analysis. Several clues as to how insulin regulates ALA-S transcription were determined. The inhibitory effect is achieved at physiological concentrations but much higher proinsulin doses are needed. Insulin's effect is rapid, quite specific, and protein synthesis is not required. Moreover, ALA-S mRNA half-life is not modified by the presence of the peptidic hormone. Our results demonstrate that the insulin effect is dominant; it overrides 8-CPT-cAMP plus phenobarbital-mediated induction. Also, insulin requires the activation of protein kinase C to exert its full effect. On the other hand, a 870-bp fragment of the ALA-S promoter region is able to sustain the inhibition of CAT expression in plasmid-transfected HepG2 cells. Thus, these results indicate that insulin plays an important role in regulating ALA-S expression by inhibiting its transcription.
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PMID:Insulin inhibits delta-aminolevulinate synthase gene expression in rat hepatocytes and human hepatoma cells. 980 96

Peroxisomal beta-oxidation (POX) of fatty acids is important in lipid catabolism and thermogenesis. To investigate the effects of peroxisome proliferators on peroxisomal and mitochondrial beta-oxidation in piglet tissues, newborn pigs (1-2 days old) were allowed ad libitum access to milk replacer supplemented with 0.5% clofibric acid (CA) or 1% aspirin for 14 days. CA increased ratios of liver weight to body weight (P < 0.07), kidney weight to body weight (P < 0.05), and heart weight to body weight (P < 0.001). Aspirin decreased daily food intake and final body weight but increased the ratio of heart weight to body weight (P < 0.01). In liver, activities of POX, fatty acyl-CoA oxidase (FAO), total carnitine palmitoyltransferase (CPT), and catalase were 2.7-, 2.2-, 1.5-fold, and 33% greater, respectively, for pigs given CA than for control pigs. In heart, these variables were 2.2-, 4.1-, 1.9-, and 1.8-fold greater, respectively, for pigs given CA than for control pigs. CA did not change these variables in either kidney or muscle, except that CPT activity was increased approximately 110% (P < 0.01) in kidney. Aspirin increased only hepatic FAO and CPT activities. Northern blot analysis revealed that CA increased the abundance of catalase mRNA in heart by approximately 2.2-fold. We conclude that 1) POX and CPT in newborn pigs can be induced by peroxisomal proliferators with tissue specificity and 2) the relatively smaller induction of POX in piglets (compared with that in young or adult rodents) may be related to either age or species differences.
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PMID:Differential induction of peroxisomal beta-oxidation enzymes by clofibric acid and aspirin in piglet tissues. 1164 Nov 28

Fatty acids may promote type 2 diabetes by altering insulin secretion from pancreatic beta cells, a process known as lipotoxicity. The underlying mechanisms are poorly understood. To test the hypothesis that peroxisome proliferator-activated receptor alpha (PPARalpha) has a direct effect on islet function, we treated INS-1 cells, an insulinoma cell line, with a PPARalpha adenovirus (AdPPARalpha) as well as the PPARalpha agonist clofibric acid. AdPPARalpha-infected INS-1 cells showed PPARalpha agonist- and fatty acid-dependent transactivation of a PPARalpha reporter gene. Treatment with either AdPPARalpha or clofibric acid increased both catalase activity (a marker of peroxisomal proliferation) and palmitate oxidation. AdPPARalpha induced carnitine-palmitoyl transferase-I (CPT-I) mRNA, but had no effect on insulin gene expression. AdPPARalpha treatment increased cellular triglyceride content but clofibric acid did not. Both AdPPARalpha and clofibric acid decreased basal and glucose-stimulated insulin secretion. Despite increasing fatty acid oxidation, AdPPARalpha did not increase cellular ATP content suggesting the stimulation of uncoupled respiration. Consistent with these observations, UCP2 expression doubled in PPARalpha-treated cells. Clofibric acid-induced suppression of glucose-simulated insulin secretion was prevented by the CPT-I inhibitor etomoxir. These data suggest that PPARalpha-stimulated fatty acid oxidation can impair beta cell function.
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PMID:PPARalpha suppresses insulin secretion and induces UCP2 in insulinoma cells. 1203 69

Fish easily accumulate n-3 PUFA of exogenous origin, but the underlying mechanisms are not well established in the whole animal. This study was undertaken to investigate whether this feature was physiologically associated with mitochondrial and peroxisomal capacities that differentially affect FA oxidation. For this purpose, peroxisomal FA oxidation was increased by treating rainbow trout with fenofibrate, which strongly stimulates the peroxisome proliferator-activated receptor-a in rodents. Diets containing EPA and DHA, with or without fenofibrate added, were administered to male trout for 12 d. After treatment, neither liver hypertrophy nor accumulation of fat was apparent within the liver and muscle cells. However, fenofibrate treatment decreased the contents of EPA and DHA in the liver, white muscle, and intraperitoneal fat tissue, which represented (per whole body) at least 280 mg less than in controls. Carnitine-dependent palmitate oxidation rates, expressed per gram of liver, were slightly increased by fenofibrate when measured from tissue homogenates and were unchanged when calculated from isolated mitochondria, relative to control fish. The treatment altered neither carnitine palmitoyltransferase I activity rates, expressed per gram of liver, nor the sensitivity of the enzyme to malonyl-CoA inhibition, but did increase the malonyl-CoA content (+45%). Meanwhile, fenofibrate increased (by about 30%) the peroxisome-related activities, i.e., catalase, carnitine-independent palmitate oxidation, acyl-CoA oxidase, and the peroxisomal FA-oxidizing system, relative to the control group. The data strongly suggest that the induction of peroxisomal activities, some of which being able to oxidize very long chain FA, was responsible for the lower contents of EPA and DHA in the body lipids of fenofibrate-treated trout.
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PMID:Alteration of 20:5n-3 and 22:6n-3 fat contents and liver peroxisomal activities in fenofibrate-treated rainbow trout. 1566 60

Subfractionation of clarified cotyledon homogenates of cotton (Gossypium hirsutum L.) seedlings on sucrose gradients revealed a single coincident peak of cholinephosphotransferase (EC 2.7.8.2) (CPT) and ethanolaminephosphotransferase (EC 2.7.8.1) (EPT) activities, which equilibrated with the main peak of Antimycin A-insensitive NADH:cytochrome c reductase (CCR) activity. The small percentage of CPT and EPT activities (less than 5% of the total) in glyoxysome-enriched pellets equilibrated with cytochrome c oxidase activity, not with catalase activity. Preincubation of microsomes (containing 83% of total CPT and EPT activities) in 0.2 millimolar MgCl(2) followed by subfractionation on sucrose gradients resulted in peak CPT and EPT activities equilibrating with peak CCR activity at 24% (w/w) sucrose. Preincubation of microsomes with (14)C-CDPcholine (or (14)C-CDPethanolamine) resulted in synthesis and incorporation of (14)C-phosphatidylcholine (PC) (or (14)C-phosphatidylethanolamine, PE) into membranes at the same density. Increasing the Mg(2+) concentration to 2.0 millimolar facilitated binding of ribosomes and caused a concomitant shift in density (to 34% w/w sucrose) of peak CPT, EPT, and CCR activities. Under these conditions, newly synthesized and incorporated (14)C-PC (or PE) was recovered in these membranes. Transmission electron microscopy of this fraction confirmed binding of ribosomes to membranes. Radiolabeling in vivo of cotyledons with [methyl-(14)C] choline chloride or [1,2 ethanolamine-(14)C] ethanolamine hydrochloride resulted in a linear incorporation of radiolabel into PC or PE in a time dependent manner. Subfractionation of homogenates of radiolabeled cotyledons on sucrose gradients showed that membranes sedimenting at 24% (w/w) sucrose (ER) contained the majority of radiolabeled PC and PE with a minor peak at 40% (w/w) sucrose (mitochondria), but no radioactive PC or PE was recovered in glyoxysomes. These results indicate that ER in cotyledons of germinated cotton seedlings is the primary subcellular site of PC and PE synthesis. This is similar to the situation in endosperm tissue but distinctly different from root and hypocotyl tissue where Golgi are a major subcellular site of PC and PE synthesis.
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PMID:Intracellular localization of phosphatidylcholine and phosphatidylethanolamine synthesis in cotyledons of cotton seedlings. 1666 83

To investigate the relationship between fenofibrate (FF) and oxidative stress, enzymatic, histopathological, and molecular biological analyses were performed in the liver of male F344 rats fed 2 doses of FF (Experiment 1; 0 and 6000 ppm) for 3 weeks and 3 doses (Experiment 2; 0, 3000, and 6000 ppm) for 9 weeks. FF treatment increased the activity of enzymes such as carnitine acetyltransferase, carnitine palmitoyltransferase, fatty acyl-CoA oxidizing system, and catalase in the liver. However, it decreased those of superoxide dismutase in the liver in both experiments. Increased 8-hydroxy-2'-deoxyguanosine levels in liver DNA and lipofuscin accumulation were observed in the treated rats of Experiment 2. In vitro measurement of reactive oxygen species (ROS) in rat liver microsomes revealed a dose-dependent increase due to FF treatment. Microarray (only Experiment 1) or real-time reverse transcription-polymerase chain reaction analyses revealed that the expression levels of metabolism and DNA repair-related genes such as Aco, Cyp4a1, Cat, Yc2, Gpx2, Apex1, Xrcc5, Mgmt, Mlh1, Gadd45a, and Nbn were increased in FF-treated rats. These results provide evidence of a direct or indirect relationship between oxidative stress and FF treatment. In addition, increases in the expression levels of cell cycle-related genes such as Chek1, Cdc25a, and Ccdn1; increases in the expression levels of cell proliferation-related genes such as Hdgfrp3 and Vegfb; and fluctuations in the expression levels of apoptosis-related genes such as Casp11 and Trp53inp1 were observed in these rats. This suggests that cell proliferation induction, apoptosis suppression, and DNA damage due to oxidative stresses are probably involved in the mechanism of hepatocarcinogenesis due to FF in rats.
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PMID:Effect of fenofibrate on oxidative DNA damage and on gene expression related to cell proliferation and apoptosis in rats. 1726 98


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