Protein kinase A (PKA) regulatory subunit isoforms differ in their tissue specificity and functional characteristics. The isoform activated in response to glucagon signaling is not known.
PKA kinase is a tetramer of two regulatory and two catalytic subunits. The regulatory subunits block the activity of the catalytic subunits.
cAMP binds the regulatory subunits, which leads to dissociation of the tetramer into two active dimers made up of a regulatory and a catalytic subunit.