Unusual Acetylation-Dependent Reaction Cascade in the Biosynthesis of the Pyrroloindole Drug Physostigmine

Authors

  • Joyce Liu,

    1. Department of Chemical and Biomolecular Engineering and Energy Biosciences Institute, University of California, Berkeley, 2151 Berkeley Way, Berkeley, CA 94704 (USA)
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  • Tailun Ng,

    1. Department of Chemical and Biomolecular Engineering and Energy Biosciences Institute, University of California, Berkeley, 2151 Berkeley Way, Berkeley, CA 94704 (USA)
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  • Dr. Zhe Rui,

    1. Department of Chemical and Biomolecular Engineering and Energy Biosciences Institute, University of California, Berkeley, 2151 Berkeley Way, Berkeley, CA 94704 (USA)
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  • Omer Ad,

    1. Department of Chemical and Biomolecular Engineering and Energy Biosciences Institute, University of California, Berkeley, 2151 Berkeley Way, Berkeley, CA 94704 (USA)
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  • Prof. Dr. Wenjun Zhang

    Corresponding author
    1. Department of Chemical and Biomolecular Engineering and Energy Biosciences Institute, University of California, Berkeley, 2151 Berkeley Way, Berkeley, CA 94704 (USA)
    • Department of Chemical and Biomolecular Engineering and Energy Biosciences Institute, University of California, Berkeley, 2151 Berkeley Way, Berkeley, CA 94704 (USA)

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  • This research was financially supported by the Pew Scholars Program and a UC Berkeley Faculty Research Grant. We thank M. Chang (UC Berkeley) for providing a protein-expression plasmid, J. Pelton (UC Berkeley) for assisting with NMR spectroscopic analysis, and J. Skerker (UC Berkeley) for helping with genome assembly.

Abstract

Physostigmine is a parasympathomimetic drug used to treat a variety of neurological disorders, including Alzheimer’s disease and glaucoma. Because of its potent biological activity and unique pyrroloindole skeleton, physostigmine has been the target of many organic syntheses. However, the biosynthesis of physostigmine has been relatively understudied. In this study, we identified a biosynthetic gene cluster for physostigmine by genome mining. The 8.5 kb gene cluster encodes eight proteins (PsmA–H), seven of which are required for the synthesis of physostigmine from 5-hydroxytryptophan, as shown by in vitro total reconstitution. Further genetic and enzymatic studies enabled us to delineate the biosynthetic pathway for physostigmine. The pathway features an unusual reaction cascade consisting of highly coordinated methylation and acetylation/deacetylation reactions.

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