Phosphatases are an important component of phosphorylation cascades. Phosphatases are always present and always active: continually dephosphorylating their targets, making the cellular response inactive. Is an important second messenger; relays initial signalling event. Cyclic amp is synthesized from atp: atp -> camp + pp: can be produced very rapidly, in large bursts, since it is a small molecule, it can diffuse very quickly throughout the cell. Different than a target molecule being activated by phosphorylases: with camp, the cell needs to get rid of it to deactivate the response. Camp is broken down into amp in reaction catalyzed by phosphodiesterase: gets rid of the second messenger, this turns off the signal transduction pathway. Blood vessels respond to cgmp by dilating: drugs to stimulate this response work by deactivating the enzyme that convert cgmp to gmp, so cgmp levels will remain high and the response will be greater, ex.