Transfers the 4'-phosphopantetheine moiety from coenzyme A to a Ser of fatty acid acyl-carrier-protein ACP. Also modifies the D-alanyl carrier protein but fails to recognize PCP and AcpK, an acyl carrier protein of secondary metabolism. apo-[ACP] + CoA = adenosine 3',5'-bisphosphate + H(+) + holo-[ACP] Homotrimer. Belongs to the P-Pant transferase superfamily. AcpS family.