Several cyclic nucleotide phosphodiesterases (PDE2, -5, -6, -10, and -11) contain a tandem of GAF domains in their N-terminal regulatory region that are thought to mediate cAMP- or cGMP-induced stimulation of adenylyl and guanylyl cyclases. Sp-cyclic AMPS (Sp-cAMPS) is a derivative of cAMP that binds the PDE10 GAF domain (EC50 = 40 μM). It has been used to study GAF-mediated stimulation of PDE10.
