Effects of the deletion and substitution of thioesterase on bacillomycin D synthesis

Objectives The importance of thioesterase domains on bacillomycin D synthesis and the ability of different thioesterase domains to selectively recognize and catalyze peptide chain hydrolysis and cyclization were studied by deleting and substituting thioesterase domains. Results No bacillomycin D analogs were found in the thioesterase-deleted strain fmbJ-ΔTE, indicating that the TE domain was essential for bacillomycin D synthesis. Then the thioesterase in bacillomycin D synthetases was replaced by the thioesterase in bacillomycin F, iturin A, mycosubtilin, plipastatin and surfactin synthetases. Except for fmbJ-S-TE, all others were able to synthesize bacillomycin D homologs because a suitable recombination site was selected, which maintained the integrity of NRPSs. In particular, the yield of bacillomycin D in fmbJ-IA-TE, fmbJ-M-TE and fmbJ-P-TE was significantly increased. Conclusion This study expands our understanding of the TE domain in bacillomycin D synthetases and shows that thioesterase has excellent potential in the chemical-enzymatic synthesis of natural products or their analogs.