Showing papers on "Acyl-CoA published in 1990"

L‐acetylcarnitine, a substrate for chloroplast fatty acid synthesis

Abstract: . H14CO3 was not incorporated into fatty acids by isolated pea leaf chloroplasts, which, therefore, do not possess a self-contained pathway for the synthesis of fatty acids from early intermediates of the Calvin cycle. Citrate, pyruvate, acetate and L-acetylcarnitine were all shown to act as sources of acetyl groups for fatty acid synthesis by pea leaf chloroplasts. L-acetylcarnitine was the best substrate, being incorporated into fatty acids at rates that were at least five-fold higher than those achieved with the other substrates. Citrate was incorporated into fatty acids at the lowest rate, followed by pyruvate, with acetate being incorporated at the second highest rate of all. When the isolated chloroplasts were ruptured, an inhibition of L-acetylcarnitine incorporation into fatty acids was noted, whilst acetate incorporation remained unaffected. L-acetylcarnitine also increased the ratio of monoenoic: saturated fatty acids synthesized, compared with a 1:1 ratio observed when citrate, pyruvate and acetate were supplied as substrates. It is suggested that L-carnitine and carnitine acyltransferases play a central role in plant acyl CoA metabolism by facilitating the transfer of activated acyl groups across membranes (acyl CoA barriers).

Significance of catalase in peroxisomal fatty acyl-CoA beta-oxidation: NADH oxidation by acetoacetyl-CoA and H2O2.

Abstract: To clarify the significance of catalase in peroxisomes, we have examined the effect of aminotriazole treatment of rats on the activity of beta-hydroxybutyryl-CoA dehydrogenase in liver peroxisomes. When the effect of H2O2 on the dehydrogenase activity was examined using an extract of liver peroxisomes from aminotriazole-treated rats, the acetoacetyl-CoA-dependent oxidation of NADH was found to increase considerably on the addition of dilute H2O2. Such an effect of H2O2 was not seen on the beta-hydroxybutyryl-CoA-dependent reduction of NAD nor with extracts from untreated animals. We then noticed that similar NADH oxidation was caused non-enzymatically by a mixture of acetoacetyl-CoA and H2O2. The oxidation was dependent on both acetoacetyl-CoA and H2O2, and was blocked by scavengers of oxyradicals such as ascorbate and ethanol. Degradation products formed during the reaction of acetoacetyl-CoA with H2O2 had no NADH oxidizing activity, indicating that effective oxidant(s) were generated during the reaction of H2O2 with acetoacetyl-CoA. No other fatty acyl-CoA so far examined nor acetoacetate could replace acetoacetyl-CoA in this reaction. Therefore, if H2O2 were to be accumulated in peroxisomes, it would decrease both NADH and acetoacetyl-CoA, thus affecting the fatty acyl-CoA beta-oxidation system. These results, together with our previous finding that peroxisomal thiolase was significantly inactivated by H2O2 [Hashimoto, F. & Hayashi, H. (1987) Biochim. Biophys. Acta 921, 142-150] suggest that the role of catalase in peroxisomes is at least in part to protect the fatty acyl-CoA beta-oxidation system from the deleterious action of H2O2.

Synthesis of acyl-CoA thioesters

Abstract: An improved synthesis of fatty acyl coenzyme A has been developed that permits the synthesis of highly radioactive fatty acyl coenzyme A derivatives and thus can be used for the synthesis of high specific activity photoaffinity labels. Conditions were developed to solubilize the coenzyme A in anhydrous solvent for the acylation. The complete activation of fatty acid to the imidazolide is described and the acylation of the coenzyme A under anhydrous conditions was shown to result in the conversion of the fatty acid to the fatty acyl coenzyme A derivative. The synthetic product was shown by its chemical and biochemical reactivity to be the pure thioester of coenzyme A. The purification of the fatty acyl coenzyme A by reverse-phase chromatography is described. The yield of pure fatty acyl coenzyme A was essentially quantitative.Key words: acyl coenzyme A, N,N′-carbonyldiimidazole, high pressure liquid chromatography, imidazolide, synthesis.

Hypolipidemic activity of benzohydroxamic acids and dibenzohydroxamic acids in rodents

Abstract: A series of benzo- and dibenzohydroxamic acids were shown to have potent hypolipidemic activity in mice and rats lowering both serum cholesterol and triglyceride levels at 20 mg/kg/day. Selected derivatives lowered tissue lipids, i.e. liver, small intestine and aorta, and accelerated fecal lipid excretion in rats. The VLDL and LDL cholesterol content was reduced and HDL cholesterol was significantly elevated after 14 days administration, orally. The agents were not HMG CoA reductase inhibitors; however, other lipid regulator enzyme activities were inhibited, e.g. acyl CoA cholesterol acyl transferase, ATP-dependent citrate lyase and acetyl CoA synthetase. The triglyceride levels were probably reduced due to the derivatives inhibiting the enzymatic activities of sn-glycerol-3-phosphate acyl transferase and phosphatidylate phosphohydrolase.

Hydrolysis of a model surfactant as measured using ACYL coenzyme a synthetase

Abstract: Hydrolysis of a model nonionic surfactant, [1‐14C]methyl palmitate, was compared between porcine esterase and lipase using a new hydrolase assay. The assay incorporates acyl coenzyme A (CoA) synthetase to convert the hydrolytic product of methyl palmitate, palmitic acid, to its acyl CoA derivative; palmitoyl CoA is separated from unreacted substrate for quantitation by a highly efficient extraction. The assay achieves quantitative separation between product and substrate due to the high water solubility of the acyl CoA derivative, eliminating the need for time‐consuming chromatographic separations. After 60 min under optimal conditions, only 20 U/mL porcine hepatic esterase hydrolyzed 93.6+0.9% of 20μM methyl palmitate, while 100U/mL porcine pancreatic lipase was required to hydrolyze only 82.3 ±0.7% of the same substrate. While both enzymes detoxified the surfactant, esterase was more efficient, possibly indicating preferential specificity for simple monoesters; generally selective for endogenous triacyl...