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

---

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

Pyrenedodecanoyl-CoA was beta-oxidized by isolated rat liver peroxisomes at a rate which was about 50% of that observed with palmitoyl-CoA. Measurement of the quantity of NADH formed from a limiting amount of pyrenedodecanoyl-CoA suggested that it was subjected to two to three cycles of beta-oxidation. Pyrenedodecanoyl-CoA was a very poor substrate for carnitine palmitoyltransferase, exhibiting less than 1% of the rate obtained with palmitoyl-CoA; it also was a strong inhibitor of this enzyme. With rat liver microsomal alpha-glycerophosphate acyltransferase the rate of reaction with pyrenedodecanoyl-CoA was only 3-4% of that observed with palmitoyl-CoA.
...
PMID:Pyrene dodecanoic acid coenzyme A ester: peroxisomal oxidation and chain shortening. 333 62

Liver mitochondria prepared by differential centrifugation are contaminated by significant quantities of peroxisomes and microsomal fractions. 'Easily solubilized carnitine palmitoyltransferase' prepared from liver mitochondria is thought to originate from the outer surface of the mitochondrial inner membrane. We have characterized the carnitine palmitoyltransferase activities of freeze-thaw extracts of rat liver mitochondrial preparations. Chromatography on Sephadex G-100 yields two broad peaks of carnitine decanoyltransferase activity: one eluted at the end of the void volume, which can be removed (precipitated) by ultracentrifugation; the second peak represents the soluble activity and is eluted at an Mr near 70,000. The activity in the soluble peak is precipitated by an antibody raised against carnitine octanoyltransferase purified from mouse liver peroxisomes. In contrast, antibody raised against carnitine palmitoyltransferase purified from liver mitochondrial membranes had no effect (P. Brady & L. Brady, personal communication). The carnitine acyltransferase activities of the Mr-70,000 peak in the presence or absence of Tween 20 showed maximum activity with decanoyl-CoA and about one-third of this activity with palmitoyl-CoA, similar to peroxisomal carnitine octanoyltransferase. These data show that 7500 g preparations of liver mitochondria isolated by differential centrifugation are enriched by peroxisomal carnitine octanoyltransferase (approx. 20% of the protein of the fraction is peroxisomal) and indicate that this enzyme may be the one reported as 'overt' or 'easily solubilized' mitochondrial carnitine palmitoyltransferase.
...
PMID:Enzymes of carnitine acylation. Is overt carnitine palmitoyltransferase of liver peroxisomal carnitine octanoyltransferase? 334 8

The effects of octylglucoside on the substrate specificity, kinetics and aggregation state of purified carnitine palmitoyltransferase (CPT) from beef heart mitochondria were investigated and compared to the effects of Triton X-100. Conditions in which CPT can be assayed in the absence of micelles and albumin, thereby eliminating miceller effects on the kinetic parameters, are described. When octylglucoside is substituted for Triton X-100, the specificity of CPT in the forward direction shifts towards the long-chain acyl-CoAs, and large changes in the kinetic constants are observed. The K0.5 for L-carnitine varied as much as 50-fold, depending on the acyl-CoA and detergent used. At pH 8.0 and 200 microM palmitoyl-CoA, the K0.5 for L-carnitine is 4.9 mM in 12 mM octylglucoside and 0.2 mM in 0.1% Triton X-100. Octylglucoside enhances the activity of CPT with long-chain acyl-CoA and lowers the K0.5 for these substrates. At pH 6.0, the K0.5 for palmitoyl-CoA is 24.2 microM in 0.1% Triton X-100, in contrast to 3.1 microM in 12 mM octylglucoside. Octylglucoside is a competitive inhibitor of CPT with octanoyl-CoA as substrate with a Ki of 15 mM. Nonlinear kinetics for both acyl-CoAs and L-carnitine are observed when the concentration of octylglucoside is reduced to less than half of its critical micellar concentration (cmc). Gel filtration of CPT in octylglucoside below its cmc gives a single protein peak with a molecular mass of ca. 660,000 daltons.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Effects of octylglucoside and triton X-100 on the kinetics and specificity of carnitine palmitoyltransferase. 336 98

Fatty acid metabolites (long-chain esters of CoA and carnitine) which collect in ischemic myocardium can form amphiphiles capable of disrupting subcellular performance. It is important to document the role of these amphiphiles in intact tissue. D-Octanoylcarnitine was chosen because of its previously described effects on inhibiting palmitoylcarnitine transferase (PCT-II) in in vitro and in vivo liver preparations. This inhibition will shift tissue levels of CoA and carnitine intermediates and thus alter amphiphile levels. The compound's actions in cardiac muscle are unknown. Dose response curves were developed in intact hearts to test the influence of D-octanoylcarnitine at pharmacological concentrations. Measurements were obtained in working, extracorporeally perfused, swine hearts. Drug was administered either systemically (IV) or via direct intracoronary (IC) infusions into the left anterior descending coronary circulation. Excess fatty acids were provided to ensure adequate fatty acid substrate for oxidation. Coronary flow was controlled at aerobic levels. Systemic administration of D-octanoylcarnitine (0.8-6.8 mM) resulted in transient peripheral hypotension which caused correlative decreases in 14CO2 production from labeled palmitate. Infusion of D-octanoylcarnitine (0.5-3.9 mM) IC did not cause appreciable hypotension and was not associated with suppression of fatty acid oxidation. No build-up of carnitine esters was noted in treated hearts but acyl CoA levels were reduced (p less than or equal to 0.002). This latter finding was modestly related to increasing dose schedule of the compound in the IC group. The lack of suppression in fatty acid oxidation argues against significant inhibition of PCT II and lessens the attractiveness of using D-octanoylcarnitine in intact myocardium to selectively block fatty acid utilization at this locus.
...
PMID:Effects of (+)-octanoylcarnitine in intact myocardium. 337 43

The effects of sodium-(E)-3-(4-(3-pyridylmethyl)phenyl)-2-methyl propenoate (OKY-1581) and (E)-3-(4-(imidazolylmethyl)phenyl)-2-propenoic acid (OKY-046), potent inhibitors to thromboxane A2 synthetase, on peroxisomal beta-oxidation and on lipid levels of liver and serum in the rat were studied. When the animals were administered with OKY-1581 at the dose levels of 100 and 500 mg/kg body weight for 2 weeks, the activity of peroxisomal beta-oxidation increased 2.2- and 6.3-fold respectively. Catalase activity increased 1.3-fold, whereas D-amino acid oxidase (DAAO) and urate oxidase activities did not change. Carnitine acetyltransferase and carnitine palmitoyltransferase activities also increased 2.2- - 4.1-fold and 2.7- - 4.2-fold respectively. These changes of the enzymes related to lipid metabolism were also confirmed by the results of a cell fractionation study. Moreover, the induction of peroxisome proliferation-associated polypeptide having a molecular weight of 80000, which is a bifunctional enzyme in the peroxisomal beta-oxidation system was also observed electrophoretically in the light mitochondrial fraction of the liver of OKY-1581-treated rat. The contents of triglyceride and cholesterol in the serum decreased. These results indicated that the action of OKY-1581 in enhancing hepatic peroxisomal-oxidation is similar to that of a potent hypolipidemic peroxisome proliferator such as clofibrate. On the other hand, differing from OKY-1581, OKY-046 at the dose level of 500 mg/kg for 2 weeks showed no effect on serum and liver lipid levels and on the activities of the peroxisomal enzymes, including a cyanide-insensitive fatty acyl-CoA oxidizing system and carnitine acetyl transferase.
...
PMID:Hypolipidemic effect and enhancement of peroxisomal beta-oxidation in the liver of rats by sodium-(E)-3-(4-(3-pyridylmethyl)phenyl)-2-methyl propenoate (OKY-1581), a potent inhibitor of TxA2 synthetase. 357 15

Carnitine palmitoyltransferase (CPT) is a mitochondrial-inner-membrane enzyme, with activities located on both the outer and inner sides of the membrane. The inhibition of CPT by bromopalmitate derivatives was studied in intact hepatic mitochondria (representing CPT-A activity, the outer enzyme), in inverted submitochondrial vesicles (representing CPT-B, the inner enzyme), and in purified hepatic CPT. Bromopalmitoyl-CoA had an I50 (concentration giving 50% inhibition of CPT activity) of 0.63 +/- 0.08 microM in intact mitochondria and 2.44 +/- 0.86 microM in inverted vesicles. Preincubation of mitochondria with bromopalmitoyl-CoA decreased V max. for both CPT-A and CPT-B. Sonication decreased sensitivity to bromopalmitoyl-CoA, and solubilization with Triton abolished sensitivity at the concentrations used (0-10 microM). Purified CPT had a bromopalmitoyl-CoA I50 of 353 microM in aqueous buffer, 67 microM in 20% dimethyl sulphoxide, 45 microM in phosphatidylcholine liposomes and 26 microM in cardiolipin liposomes. Increasing [carnitine] at constant bromopalmitoyl-CoA concentrations or increasing [bromopalmitoyl-CoA] in the preincubation resulted in increased inhibition of purified CPT. 2-Tetradecylglycidyl-CoA and malonyl-CoA did not offer measurable protection against bromopalmitoyl-CoA inhibition of the purified CPT, suggesting a different site of interaction of bromopalmitoyl-CoA with CPT. The data suggest that the sensitivity of CPT to bromopalmitoyl-CoA may be modulated by membrane environment and assay conditions.
...
PMID:Characterization of hepatic carnitine palmitoyltransferase. Use of bromoacyl derivatives and antibodies. 359 21

The enzyme targets for chlorpromazine inhibition of rat liver peroxisomal and mitochondrial oxidations of fatty acids were studied. Effects of chlorpromazine on total fatty acyl-CoA synthetase activity, on both the first and the third steps of peroxisomal beta-oxidation, on the entry of fatty acyl-CoA esters into the peroxisome and on catalase activity, which allows breakdown of the H2O2 generated during the acyl-CoA oxidase step, were analysed. On all these metabolic processes, chlorpromazine was found to have no inhibitory action. Conversely, peroxisomal carnitine octanoyltransferase activity was depressed by 0.2-1 mM-chlorpromazine, which also inhibits mitochondrial carnitine palmitoyltransferase activity in all conditions in which these enzyme reactions are assayed. Different patterns of inhibition by the drug were, however, demonstrated for both these enzyme activities. Inhibitory effects of chlorpromazine on mitochondrial cytochrome c oxidase activity were also described. Inhibitions of both cytochrome c oxidase and carnitine palmitoyltransferase are proposed to explain the decreased mitochondrial fatty acid oxidation with 0.4-1.0 mM-chlorpromazine reported by Leighton, Persico & Necochea [(1984) Biochem. Biophys. Res. Commun. 120, 505-511], whereas depression by the drug of carnitine octanoyltransferase activity is presented as the factor responsible for the decreased peroxisomal beta-oxidizing activity described by the above workers.
...
PMID:Chlorpromazine and carnitine-dependency of rat liver peroxisomal beta-oxidation of long-chain fatty acids. 359 22

Peroxisomal carnitine palmitoyltransferase was purified by solubilization using Tween 20 and KCl from the large granule fraction of the liver of clofibrate-treated chick embryo, DEAE-Sephacel and blue Sepharose CL-6B column chromatography. The peroxisomal carnitine palmitoyltransferase was an Mr 64,000 polypeptide; the mitochondrial carnitine palmitoyltransferase had a subunit molecular weight of 69,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The carnitine acetyltransferase was an Mr 64,000 polypeptide. Antibody against purified peroxisomal carnitine palmitoyltransferase reacted only with peroxisomal carnitine palmitoyltransferase, but not with mitochondrial carnitine palmitoyltransferase or carnitine acetyltransferase. In addition, anti-peroxisomal carnitine palmitoyltransferase reacted only with the protein in peroxisomes purified from chick embryo liver by sucrose density gradient centrifugation. Thus, it was confirmed that purified peroxisomal carnitine palmitoyltransferase was a peroxisomal protein. Compared with mitochondrial carnitine palmitoyltransferase, peroxisomal carnitine palmitoyltransferase was extremely resistant to inactivation by trypsin. The pH optimum of peroxisomal carnitine palmitoyltransferase was 8.5, differing from that of mitochondrial carnitine palmitoyltransferase. The Km value of peroxisomal carnitine palmitoyltransferase for palmitoyl-CoA (32 microM) was similar to that of the mitochondrial one, whereas those values for L-carnitine (140 microM), palmitoyl-L-carnitine (43 microM) and CoA (9 microM) were lower than those of mitochondrial carnitine palmitoyltransferase. Peroxisomal carnitine palmitoyltransferase exhibited similar substrate specificities in both the forward and reverse reactions, with the highest activity toward lauroyl derivatives. Furthermore, this enzyme showed relatively high affinities for long-chain acyl derivatives (C10-C16) and similar Km values (30-50 microM) for acyl-CoAs, acylcarnitine and CoA, and a constant Km value (approximately 150 microM) for carnitine. These results indicate that peroxisomal carnitine palmitoyltransferase played a role in the modulation of the intracellular CoA/long-chain acyl-CoA ratio at the hatching stage of chicken when long-chain fatty acids are actively oxidized in peroxisomes.
...
PMID:Purification and properties of peroxisomal carnitine palmitoyltransferase in chick embryo liver. 359 65

The effects of various inhibitors of carnitine palmitoyltransferase I were examined in mitochondria from rat liver and skeletal muscle. Three types of inhibitors were used: malonyl-CoA (reversible), tetradecylglycidyl-CoA and three of its analogues (irreversible), and 2-bromopalmitoyl-CoA (essentially irreversible when added with carnitine). Competitive binding studies between labeled and unlabeled ligands together with electrophoretic analysis of sodium dodecyl sulfate-solubilized membranes revealed that in mitochondria from both tissues all of the inhibitors interacted with a single protein. While the binding capacity for inhibitors was similar in liver and muscle (6-8 pmol/mg of mitochondrial protein) the proteins involved were of different monomeric size (Mr 94,000 and 86,000, respectively). Treatment of mitochondria with the detergent, octyl glucoside, yielded a soluble form of carnitine palmitoyltransferase and residual membranes that were devoid of enzyme activity. The solubilized enzyme displayed the same activity regardless of whether carnitine palmitoyltransferase I of the original mitochondria had first been exposed to an irreversible inhibitor or destroyed by chymotrypsin. It eluted as a single activity peak through four purification steps. The final product from both liver and muscle migrated as single band on sodium dodecyl sulfate-polyacrylamide electrophoresis with Mr of approximately 80,000. The data are consistent with the following model. The inhibitor binding protein is carnitine palmitoyltransferase I itself (as opposed to a regulatory subunit). The hepatic monomer is larger than the muscle enzyme. Each inhibitor interacts via its thioester group at the palmitoyl-CoA binding site of the enzyme but also at a second locus that is probably different for each agent and dictated by the chemical substituent on carbon 2. Disruption of the mitochondrial inner membrane by octyl glucoside causes inactivation of carnitine palmitoyltransferase I while releasing carnitine palmitoyltransferase II in active form. The latter is readily purified, is a smaller protein than carnitine palmitoyltransferase I, and has the same molecular weight in liver and muscle. It is insensitive to inhibitors where on or off the mitochondrial membrane.
...
PMID:Characterization of the mitochondrial carnitine palmitoyltransferase enzyme system. I. Use of inhibitors. 359 41

Exposure of rat liver mitochondrial membranes to octyl glucoside, Triton X-100, or Tween 20 solubilized an active and tetradecylglycidyl-CoA (TG-CoA)-insensitive carnitine palmitoyltransferase (presumed to be carnitine palmitoyltransferase II). The residual membranes after octyl glucoside or Triton X-100 treatment were devoid of all transferase activity. By contrast, Tween 20-extracted membranes were still rich in transferase; this was completely blocked by TG-CoA and thus was presumed to be carnitine palmitoyltransferase I. The residual carnitine palmitoyltransferase activity disappeared from the membranes upon subsequent addition of octyl glucoside or Triton X-100 and could not be recovered in the supernatant fraction. Antibody raised against purified rat liver transferase II (Mr 80,000) recognized only this protein in immunoblots from untreated liver mitochondrial membranes containing both transferases I and II. Tween 20-extracted membranes, which contained only transferase I, did not react with the antibody. Purified transferase II from skeletal muscle (also of Mr 80,000) was readily recognized by the antiserum, suggesting antigenic similarity with the liver enzyme. These and other studies on the effects of detergents on the mitochondrial [3H]TG-CoA binding protein provide further support for the model of carnitine palmitoyltransferase proposed in the preceding paper. They suggest that: 1) carnitine palmitoyltransferases I and II in rat liver are immunologically distinct proteins; 2) transferase I is more firmly anchored into its membrane environment than transferase II; 3) association of carnitine palmitoyltransferase I with a membrane component(s) is necessary for catalytic activity. While carnitine palmitoyltransferase I is a different protein in liver and muscle, it seems likely that both tissues share the same transferase II.
...
PMID:Characterization of the mitochondrial carnitine palmitoyltransferase enzyme system. II. Use of detergents and antibodies. 359 42


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---