Received Septenber 19, 1961 In previous papers (Fekete et al., 1960; Leloir et al., 1961) an enzyme was described which catalyzes glucose transfer from uridine diphoaphate glucose (UD?G) to starch or oligosaccharides. Several synthetic nucleoside diphosphate sugars have now been tested with the same enzyme preparation. They were prepared following the procedures developed by Khorana and others (Roseman, Distler, Moffatt and Khorana, 1961) with alight modifications. The most interesting result was that adenosine diphosphate glucose (ADPG) reacts about tenfold faster than UDPG. A typical experiment is shown in figure 1.