Plays a role in signal transduction by regulating the intracellular concentration of cyclic nucleotides. This phosphodiesterase catalyzes the specific hydrolysis of cGMP to 5'-GMP. Specifically regulates nitric-oxide-generated cGMP. 3',5'-cyclic GMP + H2O = GMP + H(+) Binds 1 Zn(2+) ion per subunit. Binds 2 divalent metal cations per subunit: site 1 preferentially binds zinc, while site 2 has a preference for magnesium. Tightly binds zinc. Binds 1 Mg(2+) ions per subunit. Binds 2 divalent metal cations per subunit: site 1 preferentially binds zinc, while site 2 has a preference for magnesium. Binds magnesium less tightly than zinc. Inhibited by zaprinast. Purine metabolism; 3',5'-cyclic GMP degradation; GMP from 3',5'-cyclic GMP: step 1/1. PDE5A1 and PDE5A2 are located mostly to soluble cellular fractions and some to particulate cellular fractions. Isoform PDE5A1 and isoform PDE5A2 are highly expressed in the cerebellum, hippocampus, retina, lung, heart, spleen, and thoracic artery. Isoform PDE5A1, but not isoform PDE5A2, is also abundantly expressed in the pylorus. Composed of a C-terminal catalytic domain containing two putative divalent metal sites and an N-terminal regulatory domain which contains two homologous allosteric cGMP-binding regions, A and B. Phosphorylation is regulated by binding of cGMP to the two allosteric sites. Phosphorylation by PRKG1 leads to its activation. cGMP-binding to the allosteric sites is stimulated by 3-isobutyl-1-methylxanthine (IBMX). Belongs to the cyclic nucleotide phosphodiesterase family.