cAMP is formed from:

Cyclic AMP - It consists of adenine, ribose and a phosphate. The membrane-bound enzyme Adenylate cyclase conves ATP to cAMP by cyclization. Extra information: cAMP is responsible for activation of protein kinases by phosphorylation (see fig.) cAMP is a secondary messenger and vital for regulation of many metabolic pathways in response to hormonal signal such as insulin and glucagon. Insulin will always decrease cyclic AMP and glucagon will increase its synthesis. cAMP is hydrolyzed by phosphodiesterase to 5'-AMP.