<prompt> Adenylyl cyclase is associated withGABA-aSeven transmembrane domain receptors or GPCRCholinergic receptorGlycine receptor  <response>: 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 