– Calcium/calmodulin-dependent 3′,5′-cyclic nucleotide phosphodiesterase 1B, also known as Cam-PDE 1B and PDE1B, is a cytoplasm protein that belongs to the cyclic nucleotide phosphodiesterase family and PDE1 subfamily. Phosphodiesterase-1A (PDE1A), Phosphodiesterase-1B (PDE1B), Phosphodiesterase-4B (PDE4B), and Phosphodiesterase-4A (PDE4A) are important regulators of signal transduction in striatum due to their catalysis of cyclic AMP and cyclic GMP. PDE1B is highly expressed in the striatum. It binds two divalent metal cations per subunit. Site one of PDE1B may preferentially bind zinc ions, while site two of PDE1B has a preference for magnesium and/or manganese ions. PDE1B is a cyclic nucleotide phosphodiesterase with a dual-specificity for the second messengers cAMP and cGMP, which are key regulators of many important physiological processes. It has a preference for cGMP as a substrate.