<prompt> The cyclic AMP is inactivated by the action of which specific enzyme?PhosphodiesterasePhosphateProtein kinaseAdenyl cyclase  <response>: cAMP undergoes rapid hydrolysis catalysed by the enzyme phosphodiesterase, to 5AMP which is inactive. Caffeine and theophylline can inhibit phosphodiesterase and increase the intracellular levels of cAMP. 