The function of acyl carrier protein in the synthesis of membrane-derived oligosaccharides does not require its phosphopantetheine prosthetic group.

An enzyme system catalyzing the synthesis of the beta 1,2-linked glucan backbone of the membrane-derived oligosaccharides of Escherichia coli from UDP-glucose has an essential requirement for the E. coli acyl carrier protein (ACP). This finding was surprising, because all other characterized functions of ACP involve acyl thioester residues linked to the phosphopantetheine moiety covalently bound to ACP. We now report that the activity of ACP in the synthesis of membrane-derived oligosaccharides is not altered by treatment with the sulfhydryl reagent N-ethylmaleimide nor by complete removal of the phosphopantetheine residue by treatment with a specific phosphodiesterase. The function of ACP in the synthesis of membrane-derived oligosaccharides is thus clearly different from that involved in lipid biosynthesis. We have nevertheless found that the same molecular species of ACP that undergo enzymic acylation with long-chain fatty acid residues also function in the synthesis of membrane-derived oligosaccharides.