Hydrolyzes cAMP to 5'-AMP. Plays an important regulatory role in modulating the intracellular concentration of cAMP, thereby influencing cAMP-dependent processes. May coordinate responses to nutritional stress, ensuring optimal competence development. 3',5'-cyclic AMP + H2O = AMP + H(+) Binds 2 Fe(2+) ions per subunit. Mutants show increased levels of cellular cAMP. Belongs to the cyclic nucleotide phosphodiesterase class-III family.