Glucuronyl C4 dehydrogenation by the radical SAM enzyme BlsE involved in blasticidin S biosynthesis

Here we report functional investigation of the radical S-adenosylmethionine enzyme BlsE by using cytosylglucuronamide (CGM), which is the amide analog of cytosylglucuronic acid (CGA), an intermediate involved in blasticidin S biosynthesis. We showed that, instead of decarboxylation of CGA reported previously, BlsE catalyzes C4'-dehydrogenation of CGM, and the resulting ketone is acted on by an aminotransferase BlsH to install the C4'-amino group, which uses L-Asp as the amino donor.