Acetyl-CoA-ACP Transacylase is an enzyme of fatty acid biosynthesis that catalyzes the transfer of acyl carrier protein (ACP) to acetyl-CoA in the reaction below (Figure 18.24). Acetyl-ACP is the initial two carbon unit onto which the initial malonyl-ACP is added to form -ketoacyl-ACP.

Acetyl-CoA + ACP <=> Acetyl-ACP + CoASH