Many second messenger systems activate kinases, enzymes that transfer a phosphate group from ATP to a protein. The phosphorylation of proteins sets off a series of intracellular events that lead to the ultimate cellular response.
Explanation:
For example, the second messenger cAMP activates the protein kinase A (PKA), which catalyzes the phosphorylation of other proteins.
The second messenger Ca²⁺ forms an active complex with a protein called calmodulin. This complex activates CaM kinases, that phosphorylate a group of target proteins, regulating its activities.
