Oxygen heterocycles—in particular, tetrahydropyrans (THPs) and tetrahydrofurans—are common structural features of many biologically active polyketide natural products. Mupirocin is a clinically important antibiotic isolated from Pseudomonas fluorescens and is assembled on a THP ring, which is essential for bioactivity. However, the biosynthesis of this moiety has remained elusive. Here, we show an oxidative enzyme-catalysed cascade that generates the THP ring of mupirocin. Rieske non-haem oxygenase (MupW)-catalysed selective oxidation of the C8–C16 single bond in a complex acyclic precursor is combined with an epoxide hydrolase (MupZ) to catalyse the subsequent regioselective ring formation to give the hydroxylated THP. In the absence of MupZ, a five-membered tetrahydrofuran ring is isolated, and model studies are consistent with cyclization occurring via an epoxide intermediate. High-resolution X-ray crystallographic studies, molecular modelling and mutagenesis experiments of MupZ provide insights into THP ring formation proceeding via an anti-Baldwin 6-endo-tet cyclization.
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The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request. X-ray crystallographic data are available in the EMBL-EBI PDB under accession number 6FXD.
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We are grateful to the BBSRC and EPSRC for funding through the Bristol Centre for Synthetic Biology (BB/L01386X/1), and the BBSRC for funding through BB/M012107/1 and BB/R007853/1, as well as a David Phillips Fellowship (BB/M026280/1) to M.W.v.d.K. We thank M. Malaysia for a scholarship to N.A.B., and H. P. Schweizer for kindly providing plasmids for gene inactivation and complementation.
The authors declare no competing interests.
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Wang, L., Parnell, A., Williams, C. et al. A Rieske oxygenase/epoxide hydrolase-catalysed reaction cascade creates oxygen heterocycles in mupirocin biosynthesis. Nat Catal 1, 968–976 (2018). https://doi.org/10.1038/s41929-018-0183-5
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