Flavoproteins catalyse a diversity of fundamental redox reactions and are one of the most studied enzyme families1,2. As monooxygenases, they are universally thought to control oxygenation by means of a peroxyflavin species that transfers a single atom of molecular oxygen to an organic substrate1,3,4. Here we report that the bacterial flavoenzyme EncM5,6 catalyses the peroxyflavin-independent oxygenation–dehydrogenation dual oxidation of a highly reactive poly(β-carbonyl). The crystal structure of EncM with bound substrate mimics and isotope labelling studies reveal previously unknown flavin redox biochemistry. We show that EncM maintains an unexpected stable flavin-oxygenating species, proposed to be a flavin-N5-oxide, to promote substrate oxidation and trigger a rare Favorskii-type rearrangement that is central to the biosynthesis of the antibiotic enterocin. This work provides new insight into the fine-tuning of the flavin cofactor in offsetting the innate reactivity of a polyketide substrate to direct its efficient electrocyclization.
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Protein Data Bank
The EncM sequence is deposited in GenBank under accession number AAF81732.1. The structures for proteins described in this paper have been deposited in the Protein Data Bank under accession numbers 3W8W (apo-EncM), 3W8X (EncM with bound 26) and 3W8Z (EncM with bound 4). Data for the crystallized substrate analogues are deposited in the Cambridge Crystallographic Data Centre under accession numbers CCDC 922822 (4), CCDC 922821 (10) and CCDC 949270 (26).
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We thank M. Bowman for technical assistance; Y. Su for mass spectrometric measurements; D.-H. Huang and L. Pasternack for NMR spectroscopic assistance; A. Rheingold for X-ray crystallographic analysis; and C. Hertweck for establishing the synthesis of 26. This research was supported by US National Institutes of Health grant R01AI47818 to B.S.M., National Science Foundation (NSF) awards EEC-0813570 and MCB-0645794 and the Howard Hughes Medical Institute for grants to J.P.N., NSF grant CHE-1213620 to B.P., and fellowships to R.T. from the Deutsche Forschungsgemeinschaft (TE 931/1-1) and to A.M. from the Japan Society for the Promotion of Science (21-644).
The authors declare no competing financial interests.
This file contains Supplementary Information, which is divided into parts 1 and 2: (1) Supplementary Figures 1-26, Supplementary Tables 1-17, Supplementary Text and Data (pages 3-58) and (2) NMR spectra of all chemically synthesized compounds (pages 60-86), see Contents 1 and 2 (page 59) for more details. (PDF 10595 kb)
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Teufel, R., Miyanaga, A., Michaudel, Q. et al. Flavin-mediated dual oxidation controls an enzymatic Favorskii-type rearrangement. Nature 503, 552–556 (2013). https://doi.org/10.1038/nature12643
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