Adenylyl cyclase, a membrane-associated enzyme activated by the GTP-bound alpha subunit, catalyses the second messenger cAMP from ATP molecules, is a typical target of activated G proteins. In humans, cAMP has a role in sensory processing, hormone production, and nerve transmission, among other things.
Another typical target of activated G proteins is phospholipase C. From the membrane lipid phosphatidylinositol, this membrane-associated enzyme catalyses the production of not one but two-second messengers, DAG and IP3. This route is essential for a wide range of human physiological functions. Platelet thrombin receptors, for example, employ this route to aid blood clotting.