Cytosolic 5'-nucleotidase IA (NT5C1A) catalyzes the hydrolysis of (deoxy)cytidine monophosphate, thymidine monophosphate and (deoxy)uridine monophosphate to the corresponding nucleosides plus orthophosphate. The enzyme is allosterically activated by ADP (Hunsucker et al. 2001). The human enzyme is inferred to be a homotetramer with one Mg++ ion bound per subunit based on its similarity to the pigeon heart enzyme (Bianchi and Spychala 2003; Sala-Newby et al. 1999; Skladanowski and Newby 1990).