In summary, we have demonstrated that WT-LlNDT-2 catalyzes the formation of ribonucleosides and 2′-fluoro-2′deoxynucleosides in a one-step and environmentally benign process. This expands the substrate repertoire of the nucleoside transferases and provides the basis for further development for the step-efficient preparation of 2′-modified nucleoside scaffolds with engineered variants, such as those found in the building blocks of therapeutic oligonucleotides and antiviral/anti-cancer nucleosides. 14 guidance and advice with protein purification. We also thank Mr Sam Hart and Dr Johan P.