Phosphodiesterase

PDE substrate specificities by enzyme family. Both means it hydrolyzes both cAMP and cGMP.

Classification and nomenclature

The PDE superfamily of enzymes is classified into 11 families, namely PDE1-PDE11, in mammals. The classification is based on:

• amino acid sequences
• substrate specificities
• regulatory properties
• pharmacological properties
• tissue distribution.

Clinical significance
phosphodiesterase enzymes are often targets for pharmacological inhibition due to their unique tissue distribution, structural properties, and functional properties. ^[8]
Inhibitors of PDE can prolong or enhance the effects of physiological processes mediated by cAMP or cGMP by inhibition of their degradation by PDE

http://en.wikipedia.org/wiki/Phosphodiesterase#Clinical_significance