Background：

This gene encodes one of the catalytic subunits of protein kinase A， which exists as a tetrameric holoenzyme with two regulatory subunits and two catalytic subunits， in its inactive form. cAMP causes the dissociation of the inactive holoenzyme into a dimer of regulatory subunits bound to four cAMP and two free monomeric catalytic subunits. Four different regulatory subunits and three catalytic subunits have been identified in humans. cAMP-dependent phosphorylation of proteins by protein kinase A is important to many cellular processes， including differentiation， proliferation， and apoptosis.