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

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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.