Adenylyl cyclase is associated with

Adenylyl cyclase is a transmembrane protein, and it crosses the membrane 12 times. Ten isoforms of this enzyme have been described and each can have distinct regulatory propeies, permitting the cAMP pathway to be customized to specific tissue needs. Notably, stimulatory heterotrimeric G proteins (Gs) activate, while inhibitory heterotrimeric G proteins (Gi) inactivate adenylyl cyclase (Figure 2-28). When the appropriate ligand binds to a stimulatory receptor, a Gs a subunit activates one of the adenylyl cyclases.(Ref: Ganong&;s review of medical physiology 23rd edition Page no: 56)