PDE1C is a member of the phosphodiesterases (PDE) family which catalyzes the hydrolysis of cyclic nucleotides cAMP and cGMP to the corresponding nucleoside 5-prime-monophosphates. PDE1C binds both cAMP and cGMP with high affinity and hydrolyzes both substrates with similar rates of catalysis. PDE1C is a calmodulin-dependent PDE and is stimulated by calcium-calmodulin complex. PDE1C is expressed at high levels in human cardiac myocytes with an intracellular distribution distinct from that of other phosphodiesterases. PDE1C levels decrease in all conditions that inhibited cell proliferation and PDE1C is a useful marker in studying the dynamics of proliferation and migration of various cells.