6. protein kinase cyclic adenosine monophosphate (or cAMP), cyclic guanosine monophosphate or cGMP), inositol triphosphate (or InsP3), diacylglycerol or DG)and Cat 2+ The different classes of protein kinases share a common core with high amino acid homology.6. protein kinase • The different classes of protein kinases share a common core with high amino acid homology. • cyclic adenosine monophosphate (or cAMP), cyclic guanosine monophosphate (or cGMP), inositol triphosphate (or InsP3), diacylglycerol (or DG) and Ca2＋