Regulation of PDE5 activity by cGMP binding and phosphorylation

First paragraph (this article has no abstract)

cGMP/PKG signaling pathway has been implicated in regulation of such physiological processes as smooth muscle relaxation and neuronal plasticity. The amplitude and duration of the cGMP signal is controlled by cGMP-specific, cGMP-binding phosphodiesterase (PDE5), which is highly expressed in all types of smooth muscle and cerebellar Purkinje cells. PDE5 has two highly homologous domains in its N-terminal end, recently named GAF A and GAF B based on their sequence homology with similar motifs in a wide group of proteins. The functional roles for these domains in regulation of PDE5 activity has not been fully understood.