pede4dThe PDE4 family contains four genes (PDE4A to PDE4D), only PDE4A, PDE4B, and PDE4D are expressed in the heart, each of which regulates different cAMP-dependentThe N-terminus conserved domain UCR1 and UCR2 mentioned above play an important role in dimerization of PDE4D and in the regulation of the catalytic domain [13],