The function of PDE4A (phosphodiesterase 4A, Ensembl gene identifier ENSG00000065989) is as follows. Hydrolyzes the second messenger 3',5'-cyclic AMP (cAMP), which is a key regulator of many important physiological processes. . [Isoform 1]: Efficiently hydrolyzes cAMP. . [Isoform 2]: Efficiently hydrolyzes cAMP. . [Isoform 3]: Efficiently hydrolyzes cAMP. The phosphodiesterase activity is not affected by calcium, calmodulin or cyclic GMP (cGMP) levels. Does not hydrolyze cGMP. . [Isoform 4]: Efficiently hydrolyzes cAMP. . [Isoform 6]: Efficiently hydrolyzes cAMP. {ECO:0000269|PubMed:11306681, ECO:0000269|PubMed:15738310, ECO:0000269|PubMed:17727341}. [Isoform 7]: Efficiently hydrolyzes cAMP. .