Increased activity of phosphodiesterase in a target cell would decrease its level of

The answer is cAMP or cyclic adenosine monophosphate. This is a derivative of ATP or adenosine triphosphate. It is a second messenger which is important in biological processes. This is used in signal transduction intracellularly, conveying the cAMP dependent pathway. This is formed from ATP through the action of the enzyme adenylate cyclase. Intracellular transduction can be used by hormones to exert its effects, regulation of ion channels, this can be used to activate protein kinases.