This polyketide synthase enzyme forms the (S)-2-methylbutanoate side chain during lovastatin biosynthesis by the filamentous fungus Aspergillus terreus. The overall reaction comprises a single condensation reaction followed by alpha-methylation, beta-ketoreduction, dehydration, and alpha,beta-enoyl reduction.
enzyme LovF synthesizes the alpha-S-methylbutyrate side chain that is subsequently transferred to monacolin J to yield the cholesterol-lowering natural product lovastatin. The diketide product of LovF is offloaded from the LovF acyl carrier protein domain by the dissociated acyltransferase LovD. LovD primarily interacts with the acyl carrier protein domain of LovF and the protein-protein interactions lead to highly efficient transfer of the diketide product. The catalytic efficiency is enhanced nearly one millionfold when LovF is used as the acyl carrier instead of N-acetylcysteamine