Calmodulin-dependent cyclic nucleotide phosphodiesterase with a dual specificity for cAMP and cGMP, which are key regulators of many important physiological processes (PubMed:8810348). Exhibits high affinity for both cAMP and cGMP (By similarity). Modulates the amplitude and duration of the cAMP signal in sensory cilia in response to odorant stimulation, hence contributing to the generation of action potentials. Regulates smooth muscle cell proliferation. Regulates the stability of growth factor receptors, including PDGFRB (Probable). a nucleoside 3',5'-cyclic phosphate + H2O = a nucleoside 5'-phosphate + H(+) 3',5'-cyclic GMP + H2O = GMP + H(+) 3',5'-cyclic AMP + H2O = AMP + H(+) Binds 2 divalent metal cations per subunit. Site 1 may preferentially bind zinc ions. Binds 2 divalent metal cations per subunit. Site 2 has a preference for magnesium ions. Type I PDE are activated by the binding of calmodulin in the presence of Ca(2+) (PubMed:8810348). Different splice variants may have different sensitivities to Ca(2+) (PubMed:8810348). Exhibits a higher sensitivity to Ca(2+) stimulation than isoforms 1 and 2 (PubMed:8810348). Homodimer. Highly expressed in testis and at moderate levels in heart. Expressed at a moderate level in brain, the cerebellum, testis, heart and olfactory epithelium. Highly expressed in olfactory epithelium and at very low levels, if any, in other tissues (PubMed:8810348). In the cochlea, expressed in the inner and outer hair cells (at protein level) (PubMed:29860631). In the brain, highly expressed in the neurons of the granule layer of the cerebellum, some Purkinje cells, the central amygdaloid nucleus, and the interpolar spinal trigem nucleus and, at moderate levels, in the glomerular and external plexiform layer of the olfactory bulb as well as in parts of the caudate-putamen and olfactory tubercle (PubMed:8810348). PDE1C4 and PDE1C5 isoforms differ at the level of the 3'-UTR. Belongs to the cyclic nucleotide phosphodiesterase family. PDE1 subfamily.