Enzymatic Synthesis of Molecular Skeletons of Complex Antitumor Antibiotics with Non-ribosomal Peptide Synthetases

Abstract

Nonribosomal peptide synthetase (NRPS) is a programmable modular machinery which produces a number of biologically active small–molecule peptides. Recent progress on understanding the catalytic mechanism of NRPS enabled us to engineer this complex catalytic system. We demonstrated both in vivo and in vitro enzymatic synthesis of complex natural antitumor peptides echinomycin and saframycin. An Escherichia coli–based expression system served as a flexible yet robust platform for producing complex natural products and their analogs by deletion, mutation and swapping of a specific subunit. The excised thioesterase domain of echinomycin exhibited remarkable substrate tolerance and created a cyclic peptide library. On the other hand, saframycin NRPS catalyzed highly unusual seven–step transformations to construct a pentacyclic tetrahydro–isoquinoline skeleton.