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bioRxiv · 10.1101/2024.09.26.615303

Biosynthesis of the alpha-D-Mannosidase Inhibitor (-)-Swainsonine

Liu, S.·Batool, Z.·Hai, Y.
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Abstract

(-)-Swainsonine is a polyhydroxylated indolizidine alkaloid with potent inhibitory activity against -D-mannosidases. In this work, we successfully reconstituted swainsonine biosynthetic pathway both in vivo and in vitro. Our study unveiled an unexpected epimerization mechanism involving two -ketoglutarate-dependent non-heme iron dioxygenases (SwnH2 and SwnH1), and an unusual imine reductase (SwnN), which displays substrate-dependent stereospecificity such that the stereochemical outcome of SwnN-catalyzed iminium reduction is ultimately dictated by SwnH1-catalyzed C8-hydroxylation. We also serendipitously discovered that an O-acetyl group can serve as a detachable protecting/directing group, altering the site-selectivity of SwnH2-catalyzed hydroxylation while maintaining the stereoselectivity. Insights gained from the biochemical characterization of these tailoring enzymes enabled biocatalytic synthesis of a new polyhydroxylated indolizidine alkaloid, opening doors to the biosynthesis of diverse natural product-based glycosidase inhibitors.

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Liu, S., Batool, Z., Hai, Y.. 2024-09-27. Biosynthesis of the alpha-D-Mannosidase Inhibitor (-)-Swainsonine. https://doi.org/10.1101/2024.09.26.615303

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