Cyclic AMP (cAMP) is a secondary messenger used in cell signalling. It is synthesised from ATP by the enzyme adenylyl cyclase. It is continuously destroyed by cylcic AMP phosphodiesterases that will hydrolyze cyclic AMP to adenosine 5'monophosphate (5'-AMP) .
The concentration within a cell of cyclic AMP is normally around 10-7 however an extracellular signal can raise those levels within the cell by a factor of 20 within seconds . Production of cyclic AMP results in the activation of Protein kinase A, which triggers cellular responses by activating enzymes, stimulating cellular secretion or opening ion channels.