3’-O-β-Glycosylation of nucleoside analogues using a promiscuous bacterial glycosyltransferase

Nucleoside analogue therapeutics have a proven capability within drug discovery as antimicrobial, antiviral and antineoplastic agents. However, their efficacy can be limited by poor cellular uptake, high off target toxicity and poor bioavailability. Prodrugs of such analogues contribute to an improved pharmacokinetic profile. Herein, we explore biocatalytic glycosylation of nucleoside analogues. The activity of the nucleoside-specific 3’-O-glycosyltransferase AvpGT from Streptomyces sp. AVP053U2 is investigated against a panel of both natural and clinically relevant purine and pyrimidine nucleoside analogues. AvpGT demonstrates broad substrate promiscuity, with 16 of 22 nucleosides tested showing glycosylation by HILIC-MS. Of these, 13 nucleosides were successfully glycosylated on 25 μmol scale in 39-91% yields, including four nucleoside analogue therapeutics. Furthermore, a novel β-glucosidase, AvpGS, was identified from the same Streptomyces sp. strain, heterologously expressed, purified and shown to display high substrate promiscuity in subsequently removing glucose from the glycoconjugates.