| Modification Notes |
cAMP and cGMP are 3',5'-cyclic nucleotides that function as second messengers in a wide variety of signaling pathways throughout the cell. The hydrolysis of cAMP and cGMP to their corresponding 5'-monophosphates (5'-AMP and 5'-GMP, respectively) is catalyzed by 3',5'-cyclic nucleotide phosphodiesterases (PDEs), which provide a means of downregulating cAMP and cGMP signaling. PDE11A (phosphodiesterase 11A), also known as PPNAD2, is a 934 amino acid cytoplasmic protein that belongs to the PDE family. Expressed as four isoforms that exhibit different tissue specificity, PDE11A contains two GAF domains through which it functions to catalyze the H2O-dependent conversion of cAMP and cGMP to their hydrolyzed forms. PDE11A activity is pH-dependent and is regulated by the binding of free cGMP (which acts as an allosteric activator) to the GAF domains, an event that stimulates enzyme activity. Defects in the gene encoding PDE11A are the cause of primary pigmented nodular adrenocortical disease type 2 (PPNAD2), a bilateral adrenal defect that leads to endocrine-related Cushing syndrome. |