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Neopinone isomerase is involved in codeine and morphine biosynthesis in opium poppy


The isomerization of neopinone to codeinone is a critical step in the biosynthesis of opiate alkaloids in opium poppy. Previously assumed to be spontaneous, the process is in fact catalyzed enzymatically by neopinone isomerase (NISO). Without NISO the primary metabolic products in the plant, in engineered microbes and in vitro are neopine and neomorphine, which are structural isomers of codeine and morphine, respectively. Inclusion of NISO in yeast strains engineered to convert thebaine to natural or semisynthetic opiates dramatically enhances formation of the desired products at the expense of neopine and neomorphine accumulation. Along with thebaine synthase, NISO is the second member of the pathogenesis-related 10 (PR10) protein family recently implicated in the enzymatic catalysis of a presumed spontaneous conversion in morphine biosynthesis.

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Fig. 1: Characterized pathways for the conversion of thebaine to morphine in opium poppy.
Fig. 2: Screening of pathogenesis-related 10 (PR10) and major latex proteins (MLP) for neopinone isomerase activity.
Fig. 3: Time-course assays with codeinone or codeine incubated with COR-B alone or coupled with NISO.
Fig. 4: COR-B and NISO stoichiometry affects the production of neopine.
Fig. 5: Suppression of NISO transcript levels alters the accumulation of opiate alkaloids in opium poppy.
Fig. 6: NISO improves the production of codeine and hydrocodone in engineered yeast strains.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request. The sequences reported in this paper have been deposited in the GenBank database with accession numbers MH455205 (NISO) and MH094273 (genomic scaffold).


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We are grateful to L. Brechenmacher (Southern Alberta Mass Spectrometry Centre, University of Calgary) for assistance with the proteomics analysis. We acknowledge the expert genome sequencing and preliminary assembly services provided by the McGill University-Genome Québec Innovation Centre. This work was supported by funds awarded through the Industrial Research Assistance Program (IRAP; Project 86155) operated by the National Research Council of Canada to Epimeron Inc.

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Authors and Affiliations



M.D. performed the in vitro enzyme characterization and wrote the manuscript; X.C. discovered the enzyme and conducted the gene expression analysis; L.C. performed all yeast work; R.C. conducted virus-induced gene-silencing experiments; S.R. and S.Y. assembled the genome; J.M.H. performed high-resolution mass spectrometry, proposed the enzymatic mechanism, and edited the manuscript; P.J.F. designed and supervised the research and edited the manuscript.

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Correspondence to Peter J. Facchini.

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A patent application related to this work has been filed (PCT/CA2018/051520).

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Dastmalchi, M., Chen, X., Hagel, J.M. et al. Neopinone isomerase is involved in codeine and morphine biosynthesis in opium poppy. Nat Chem Biol 15, 384–390 (2019).

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