A divalent cation is required for activity. UDP-sugar is the best substrate, although other nucleoside-sugar diphosphates are used as substrates with similar Km values but much lower maximum velocities. Thus, this enzyme has a specificity distinct from that of ADP-sugar diphosphatase (EC
3.6.1.21). Some but not all enzymes of this class also appear to have 5'-nucleotidase (see EC
3.1.3.5) activity.