Protein kinase A (PKA) refers to a family of multimeric enzyme complexes whose activity is dependent on the level of cyclic AMP (cAMP), hence PKA is also known as cAMP-dependent protein kinase (EC 18.104.22.168). PKA has several functions in the cell, including regulation of glycogen, sugar, and lipid metabolism.
PKA is a holoenzyme complex consisting of two regulatory and two catalytic subunits. When cAMP levela are low the holoenzyme remains intact and is inactive. When the concentration of cAMP rises (e.g. as a result of adenylate cyclase activation by G protein-coupled receptors coupled to Gs, or inhibition of phosphodiesterases that degrade cAMP) cAMP binds to two binding sites on the regulatory subunits, leading to the release and activation of the catalytic subunits. The regulatory subunits of PKA are also important for localizing the kinase inside the cell. A-kinase anchor proteins (AKAPs) bind to the regulatory subunits and to cytoskeletal structures or membranes, anchoring the enzyme complex to a particular subcellular compartment. Dual-specificity A kinase-anchoring proteins (AKAP1/D-AKAP1) and (AKAP10/D-AKAP2) interact with the type I and type II regulatory subunits of PKA (Huang et al. 1997). AKAP10 additionally has two regulator of G-protein signaling (RGS) domains, giving it the potential to coordinate a signaling complex that links cAMP signaling with G-protein-coupled receptor (GPCR) signaling (Burns-Hamuro et al. 2004).