Some factors affecting chain elongation of palmityl-coA in rat liver microsomes.

The chain elongation of labeled palmityl-CoA by rat liver microsomes was studied by radio-gas liquid chromatography after the incubation of the acid in a medium containing malonyl-CoA, β-mercaptoethanol, reduced nicotinamide adenine dinucleotide (NADH), reduced nicotinamide adenine dinucleotide phosphate (NADPH), KCN and sucrose under anaerobic conditions. The activity of chain elongation of palmityl-CoA to stearic acid was increased by refeeding starved rats. The activity in liver microsomes of refed rats was approximately twice greater than that of normal rats. Lipid phosphorus contents in liver microsomes of normal (15.4±0.8μg P/mg protein) and refed rats (15.3±1.6μg P/mg protein) were unchanged. However, the reaction was stimulated by the addition of sonicated dispersion of phosphatidylcholine. The stimulatory effect of the dispersion was more remarkable for refed rats than for normal ones. On the other hand, the chain elongation activity of palmityl-CoA was decreased by acetone extraction or phospholipase C treatment of liver microsomes of refed rats. The decreased activity was partially or completely restored by the addition of sonicated dispersion of phosphatidylcholine. These results suggest that phospholipids may play an important role for chain elongation reaction of fatty acids in liver microsomes of rats.