PKA (Protein Kinase-A) is an enzyme that regulates processes as diverse as growth, development, memory, and metabolism. In its inactivated state, PKA exists as a tetrameric complex of two Catalytic subunits (PKA-C) and a Regulatory (PKA-R) subunit dimer. To date, four regulatory subunits have been identified (RI-Alpha, RI-Beta, RII-Alpha and RII-Beta), which are differentially distributed in mammalian tissues. RI-Alpha and RII-Alpha are expressed ubiquitously, RI-Beta is expressed predominantly in the brain and RII-Beta is expressed primarily in brain, adrenal and adipose tissues. These R subunits define Types-I and II PKA, with both types of holoenzyme having three potential C subunits (Alpha, Beta and Gamma). The C-Alpha and Beta subunits share 93% homology and have broad tissue specificity, with C-Alpha being [...]