Acylation of carnitine and glycerophosphate in suspensions of rat liver mitochondria at varying levels of palmitate and coenzyme A

Abstract

Rates of acylation of carnitine and glycerophosphate in suspensions of isolated rat liver mitochondria were measured at varying levels of palmitate and coenzyme A in the presence of ATP. Addition of glycerophosphate caused considerable reduction in carnitine acylation at low, but not at high palmitate levels. Glycerophosphate acylation was less reduced by added carnitine. These results can be explained by a lower Km(acyl-CoA) in glycerophosphate acylation than in carnitine acylation. High levels of free coenzyme A caused inhibition of carnitine acylation, while the inhibitory effect of glycerophosphate acylation was small. Competition between palmitate and acyl-CoA for binding sites on protein (e.g., albumine added to the mitochondrial suspensions) was indicated by stimulation of carnitine acylation by palmitate with palmityl-CoA added as substrate in the absence of ATP. Refeeding a carbohydrate-rich diet to previously fasted rats resulted in increased glycerophosphate acylation and decreased carnitine acylation in isolated liver mitochondria.