Fungal indole alkaloid biogenesis through evolution of a bifunctional reductase/Diels–Alderase

Qingyun Dan, Sean A. Newmister, Kimberly R. Klas, Amy E. Fraley, Timothy J. McAfoos, Amber D. Somoza, James D. Sunderhaus, Ying Ye, Vikram V. Shende, Fengan Yu, Jacob N. Sanders, W. Clay Brown, Le Zhao, Robert S. Paton, K. N. Houk, Janet L. Smith, David H. Sherman, Robert M. Williams

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Prenylated indole alkaloids such as the calmodulin-inhibitory malbrancheamides and anthelmintic paraherquamides possess great structural diversity and pharmaceutical utility. Here, we report complete elucidation of the malbrancheamide biosynthetic pathway accomplished through complementary approaches. These include a biomimetic total synthesis to access the natural alkaloid and biosynthetic intermediates in racemic form and in vitro enzymatic reconstitution to provide access to the natural antipode (+)-malbrancheamide. Reductive cleavage of an l-Pro–l-Trp dipeptide from the MalG non-ribosomal peptide synthetase (NRPS) followed by reverse prenylation and a cascade of post-NRPS reactions culminates in an intramolecular [4+2] hetero-Diels–Alder (IMDA) cyclization to furnish the bicyclo[2.2.2]diazaoctane scaffold. Enzymatic assembly of optically pure (+)-premalbrancheamide involves an unexpected zwitterionic intermediate where MalC catalyses enantioselective cycloaddition as a bifunctional NADPH-dependent reductase/Diels–Alderase. The crystal structures of substrate and product complexes together with site-directed mutagenesis and molecular dynamics simulations demonstrate how MalC and PhqE (its homologue from the paraherquamide pathway) catalyse diastereo- and enantioselective cyclization in the construction of this important class of secondary metabolites.

Original languageEnglish (US)
Pages (from-to)972-980
Number of pages9
JournalNature Chemistry
Issue number11
StatePublished - Nov 1 2019
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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