Macrodiolide Formation by the Thioesterase of a Modular Polyketide Synthase.

Yongjun Zhou,Patrícia Prediger,Peter F Leadlay,Luiz Carlos Dias,Annabel C Murphy

doi:10.1002/ange.201500401

Yongjun Zhou, Patrícia Prediger + Show 3 more

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https://doi.org/10.1002/ange.201500401

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Abstract

Elaiophylin is an unusual C2-symmetric antibiotic macrodiolide produced on a bacterial modular polyketide synthase assembly line. To probe the mechanism and selectivity of diolide formation, we sought to reconstitute ring formation in vitro by using a non-natural substrate. Incubation of recombinant elaiophylin thioesterase/cyclase with a synthetic pentaketide analogue of the presumed monomeric polyketide precursor of elaiophylin, specifically its N-acetylcysteamine thioester, produced a novel 16-membered C2-symmetric macrodiolide. A linear dimeric thioester is an intermediate in ring formation, which indicates iterative use of the thioesterase active site in ligation and subsequent cyclization. Furthermore, the elaiophylin thioesterase acts on a mixture of pentaketide and tetraketide thioesters to give both the symmetric decaketide diolide and the novel asymmetric hybrid nonaketide diolide. Such thioesterases have potential as tools for the in vitro construction of novel diolides.

Highlights

Elaiophylin is an unusual C2-symmetric antibiotic macrodiolide produced on a bacterial modular polyketide synthase assembly line
The elaiophylin thioesterase acts on a mixture of pentaketide and tetraketide thioesters to give both the symmetric decaketide diolide and the novel asymmetric hybrid nonaketide diolide
Malonyl units; an acyltransferase (AT), which specifies the type of extender unit introduced; and an acylcarrier protein (ACP), which tethers the growing polyketide chain while it is processed by optional ketoreductase (KR), dehydratase (DH), and enoylreductase (ER) domains

Summary

Introduction

Elaiophylin is an unusual C2-symmetric antibiotic macrodiolide produced on a bacterial modular polyketide synthase assembly line. Tide monomers, which in vivo are acted upon by the TE while tethered to an adjacent ACP domain in the multienzyme assembly line, we show here that the TE can catalyze homodimerization of the synthetic pentaketide 3 b (Scheme 1) to a novel 16-membered decaketide diolide 5 (Figure 1), and we identify an intermediate that sheds light on the enzymatic mechanism.

Results

Conclusion