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. Author manuscript; available in PMC: 2020 Mar 30.
Published in final edited form as: Nat Rev Chem. 2019 Jun 12;3(7):404–425. doi: 10.1038/s41570-019-0107-1

Fig. 4. Unusual post-polyketide synthase/nonribosomal peptide synthetase enzymology.

Fig. 4

a | Enzymatic [4+2] cycloadditions during pyrroindomycin biosynthesis. Grey panel: Diels–Alder-type cyclizations catalysed by PyrE3 (orange) and PyrI4 (blue)56. New bonds formed are highlighted in red. Blue panel: six-membered rings (highlighted in blue) installed by PyrI4 homologues during abyssomycin57 and versipelostatin55 biosynthesis. b | Grey panel: TmcF catalyses a remarkable decarboxylation–dehydrogenation–oxygenation transformation to generate the epoxyketone moiety present in TMC-86A62. The new bond formed to close the epoxide ring is highlighted in red. Blue panel: select examples of natural product proteasome inhibitors that are proposed to employ TmcF homologues during their biosynthesis to install α/β-epoxyketone warhead moieties59–62. Epoxyketone moieties introduced by TmcF and its homologues are highlighted in orange.