Effect of thiolactomycin on the individual enzymes of the fatty acid synthase system in Escherichia coli.

Thiolactomycin, an antibiotic with the structure of (4S)-(2E,5E)-2,4,6-trimethyl-3-hydroxy-2,5,7-octatriene-4-++ +thiolide, selectively inhibits type II fatty acid synthases. The mode of the thiolactomycin action on the fatty acid synthase system of Escherichia coli was investigated. Of the six individual enzymes of the fatty acid synthase system, [acyl-carrier-protein] (ACP) acetyltransferase and 3-oxoacyl-ACP synthase were inhibited by thiolactomycin. On the other hand, the other enzymes were not affected by this antibiotic. The thiolactomycin inhibition of the fatty acid synthase system was reversible. As to ACP acetyltransferase, the inhibition was competitive with respect to ACP and uncompetitive with respect to acetyl-CoA. As to 3-oxoacyl-ACP synthase, the inhibition was competitive with respect to malonyl-ACP and noncompetitive with respect to acetyl-ACP. The thiolactomycin action on the fatty acid synthase system was compared with that of cerulenin.