Cyclic adenosine monophosphate

Structure of cAMP

Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3'-5'-cyclic adenosine monophosphate) is a molecule that is important in many biological processes; it is derived from adenosine triphosphate (ATP). cAMP is a second messenger, used for intracellular signal transduction, such as transferring the effects of hormones like glucagon and adrenaline, which cannot get through the cell membrane. Its main purpose is the activation of protein kinases; it is also used to regulate the passage of Ca²⁺ through ion channels.

cAMP synthesis and decomposition

cAMP is synthesized from ATP by adenylate cyclase. Adenylate cyclase is located at the cell membranes. It is activated by the hormones glucagon and adrenaline and by G protein. Liver adenylate cyclase responds more strongly to glucagon, and muscle adenylic cyclase responds more strongly to adrenaline.

cAMP decomposition into AMP is catalyzed by the enzyme phosphodiesterase. This enzyme is inhibited by caffeine, the stimulatory effect of this drug being the result of the raised cAMP levels that it causes.

Protein kinase activation

In the absence of cAMP, a protein kinase is inactive and exists as a tetramer, consisting of 2 catalytic and 2 regulatory units (C₂R₂), with the regulatory units blocking the catalytic centers of the catalytic units.

cAMP binds to specific locations on the regulatory units of the protein kinase, causing them to dissociate from the tetramer, thus activating the catalytic units so they can perform their function.

Glycogen decomposition regulation

cAMP controls many biological processes, including glycogen decomposition into glucose, and lipolysis.

Role of cAMP in bacteria

In bacteria, cAMP is produced when the level of glucose in the cell is low; it activates the production of enzymes that can supply glucose.

de:Cyclisches Adenosinmonophosphat