In: Biology
Adenyl cyclase is a enzyme that catalyze the conversion of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP). It is also knwn as adenylyl cyclase or adenylate cyclase
ATP ----------------------(adenyl cyclase)-----------------------> cAMP + pyrophosphate
Adenyl cyclase as well as cAMP are very important molecules in signal transduction. The cAMP produced by the catalization of adenyl cyclase acts as a second messenger in signal tranduction.
Adenyl cyclase is an integral membrane protein consist of two bundles of six transmembrane segments. Its two catalytic domains extend as loops into the cytoplasm. It is mainly regulated by G-protein, which is inturn coupled with membrane receptors. Whenever an external stimuli like hormones or ligands binds to G-protein coupled receptors, adenyl cyclase gets activated and as a result the cAMP is produced, which leads to an increase in the cAMP level. Some of the examples of signal tranduction pathways where adenyl cyclase involved are,
1) Hormone induction and activation of adenyl cyclase in adipose cells- If a stimulatory hormone like epinephrin, glucagon or ACTH binds to its specific receptor, it stimulates the G-protein complex and activate the production of adenyl cyclase. This adenyl cyclase synthesizes cAMP which will undergoes a series of reactions to produce the effector protein. In contrast, if an inhibitory hormone is binding to the receptor (like prostaglandin or adenosine), then no activation of adenyl cyclase or cAMP occurs. Hence no further downstream signal transduction is carried out.
2) Glycogen breakdown and synthesis- If glycogen needs to be broken down into glucose, then its signals activates the production of adenyl cyclase which in turn synthesize cAMP. This cAMP activates another protein called protein kinase A (PKA) which stimulates the enzymes that breaks glycogen down into glucose. In the absence of all these signals, glycogen synthesis occurs.