Cyclic-AMP phosphodiesterase (EC:3.1.4.17) (PDE) catalyses the hydrolysis of cAMP to the
corresponding nucleoside 5' monophosphate. On the basis of sequence
similarity, most PDEs can be grouped together [1], but 2 enzymes lie apart
from the main family and represent a second distinct class [2]: this
includes PDEs from Dictyostelium and yeast.
There is, in the central part of these enzymes, a highly conserved region
which contains three histidines.