Graduate School of Agricultural and Life Sciences, The University of Tokyo

Authors

Jie Zhang¹、Satoshi Yuzawa¹、Wei Li Thong²、Tetsuro Shinada³、Makoto Nishiyama²、Tomohisa Kuzuyama¹*

¹Graduate School of Agricultural and Life Sciences, The University of Tokyo
²Biotechnology Research Center, The University of Tokyo
³Graduate School of Science, Osaka City University

Abstract

Natural products containing an o-dialkylbenzene moiety exhibit a wide variety of bioactivities, including antibacterial, antifungal, antitumor, and antiangiogenic activities. However, the biosynthetic scheme of the o-dialkylbenzene moiety remains unclear. In this study, we identified the biosynthetic gene cluster (BGC) of compounds 1 and 2 in Streptomyces sp. SANK 60404, which contains a rare o-dialkylbenzene moiety, and successfully reconstituted the biosynthesis of 1 using 22 recombinant enzymes in vitro. Our study established a biosynthetic route for the o-tolyl group within the o-dialkylbenzene moiety, where the triene intermediate 3 loaded onto a unique acyl carrier protein (ACP) is elongated by a specific ketosynthase–chain length factor pair of a type II polyketide synthase system with the aid of a putative isomerase to be termed “electrocyclase” and a thioesterase-like enzyme in the BGC. The C₂-elongated all-trans diketo–triene intermediate is subsequently isomerized to the 6Z configuration by the electrocyclase to allow intramolecular 6π-electrocyclization, followed by coenzyme FAD/FMN-dependent dehydrogenation. Bioinformatics analysis showed that the key genes are all conserved in BGCs of natural products containing an o-dialkylbenzene moiety, suggesting that the proposed biosynthetic scheme is a common strategy to form o-dialkylbenzenes in nature.

Paper Information

Journal

: Journal of the American Chemical Society

DOI

: 10.1021/jacs.0c13378

: http://pubs.acs.org/doi/abs/10.1021/jacs.0c13378