Ribonucleosides 7 or 8 were used as representative sugar donors, with 9 and 17 used as the corresponding nucleobases (Figure ). Using 2 g/mL loading of LlNDT-2 formed the desired nucleosides 10 and 18 with 6% and 4% conversion, respectively. However, when the enzyme loading was increased, conversion to 10 (100 g/mL) and 18 (300 g/mL) increased to 96% and 29%, respectively.