A simple and sensitive cAMP phosphodiesterase assay using a modification of the Ba(OH)2-ZnSO4 precipitation method

A modification of the zinc-barium precipitation method is described for the measurement of phosphodiesterase activity. This method differs from the previous precipitation method in that it measures the appearance of the 5'-AMP product in the precipitate rather than the disappearance of the cAMP substrate from the supernatant. The method is simple, rapid, accurate and possesses a high sensitivity. It can be used to measure both the calmodulin activatable and nonactivatable forms of the enzyme. The procedure can be applied to monitoring phosphodiesterase activity throughout the purification of the enzyme from various tissues.