Natural products from thioester reductase containing biosynthetic pathways

A dual transacylation mechanism for polyketide synthase chain release in enacyloxin antibiotic biosynthesis

Polyketide synthases assemble diverse natural products with numerous important applications. The thioester intermediates in polyketide assembly are covalently tethered to acyl carrier protein domains of the synthase. Several mechanisms for polyketide chain release are known, contributing to natural product structural diversification. Here we report a dual transacylation mechanism for chain release from the enacyloxin polyketide synthase, which assembles an antibiotic with promising activity against Acinetobacter baumannii. A non-elongating ketosynthase domain transfers the polyketide chain from the final acyl carrier protein domain of the synthase to a separate carrier protein and a nonribosomal peptide synthetase condensation domain condenses it with (1S, 3R, 4S)-3, 4-dihydroxycyclohexane carboxylic acid. Molecular dissection of this process reveals that non-elongating ketosynthase domain-mediated transacylation circumvents the inability of the condensation domain to recognize the acyl carrier protein domain. Several 3, 4-dihydroxycyclohexane carboxylic acid analogues can be employed for chain release, suggesting a promising strategy for producing enacyloxin analogues.

Mining novel biosynthetic machineries of secondary metabolites from actinobacteria

Secondary metabolites produced by actinobacteria have diverse structures and important biological activities, making them a useful source of drug development. Diversity of the secondary metabolites indicates that the actinobacteria exploit various chemical reactions to construct a structural diversity. Thus, studying the biosynthetic machinery of these metabolites should result in discovery of various enzymes catalyzing interesting and useful reactions. This review summarizes our recent studies on the biosynthesis of secondary metabolites from actinobacteria, including the biosynthesis of nonproteinogenic amino acids used as building blocks of nonribosomal peptides, the type II polyketide synthase catalyzing polyene scaffold, the nitrous acid biosynthetic pathway involved in secondary metabolite biosynthesis and unique cytochrome P450 catalyzing nitrene transfer. These findings expand the knowledge of secondary metabolite biosynthesis machinery and provide useful tools for future bioengineering.

Built to bind: biosynthetic strategies for the formation of small-molecule protease inhibitors

The discovery and characterization of natural product protease inhibitors has inspired the development of numerous pharmaceutical agents.