Radical SAM enzymes in the biosynthesis of sugar-containing natural products

Carbohydrates play a key role in the biological activity of numerous natural products. In many instances their biosynthesis requires radical mediated rearrangements, some of which are catalyzed by radical SAM enzymes. BtrN is one such enzyme responsible for the dehydrogenation of a secondary alcohol in the biosynthesis of 2-deoxystreptamine. DesII is another example that catalyzes a deamination reaction necessary for the net C4 deoxygenation of a glucose derivative en route to desosamine formation. BtrN and DesII represent the two most extensively characterized radical SAM enzymes involved in carbohydrate biosynthesis. In this review, we summarize the biosynthetic roles of these two enzymes, their mechanisms of catalysis, the questions that have arisen during these investigations and the insight they can offer for furthering our understanding of radical SAM enzymology. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology.

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► BtrN is a radical SAM enzyme involved in the biosynthesis of 2-deoxystreptamine.
► DesII is a radical SAM enzyme in involved in the biosynthesis of d-desosamine.
► BtrN catalyzes a radical mediated dehydrogenation.
► DesII catalyzes either a radical mediated deamination or dehydrogenation.
► Here we review the current biosynthetic and mechanistic understanding of these enzymes.