Acyl‐acyl carrier protein as substrate of the acyltransferase of rat liver microsomes

Abstract

Acyl-acyl carrier protein (acyl-ACP) can serve as well as acyl-CoA as substrate of the 1-acyl-sn-glycero-3-phosphocholine (1-acyl-GPC) acyltransferase of rat-liver microsomes. The product of the acylation with either thioester substrate is predominantly phosphatidylcholine (PC) (92–95%). The acyl-group transferred from either myristoyl-CoA or myristoyl-ACP is located at the C-2 position of the phospholipid (PL). The apparent Km values for the myristoyl-CoA and myristoyl-ACP were 46 μM and 63 μM, and the corresponding apparent Vmax values were 1.0 and 1.6 nmol/min/mg. The rate of acylation with the acyl-ACP was unaffected by the addition of free CoA-SH. These data suggest that acyl-CoA and acyl-ACP are transferred to 1-acyl-GPC by the same or similar enzyme systems.