cAMP is a signaling molecule important for a variety of cellular functions. cAMP exerts its effects by activating the cAMP dependent protein kinase (AMPK), which transduces the signal through phosphorylation of different target proteins. The inactive holoenzyme of AMPK is a tetramer composed of two regulatory and two catalytic subunits. 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 of AMPK have been identified in humans. PKA beta (catalytic subunit) is a member of the Ser/Thr protein kinase family and is a catalytic subunit of AMPK.