A new method for measurement of cyclic AMP phosphodiesterase activity

The extreme sensitivity of chicken muscle fructose 1,6-bisphosphatase to inhibition by 5'-AMP has been utilized to develop a new method for the assay of cAMP phosphodiesterase activity. In this method, the substrate (cAMP) is first incubated with phosphodiesterase and the amount of 5'-AMP formed is then determined by measuring the degree of inhibition of fructose 1'6-bisphosphatase activity. The present method conveniently employs the spectrophotometric technique and is sensitive enough to detect the conversion of 50 pmol of cAMP to 5'-AMP in 1 ml of reaction mixture. This method is considered particularly valuable for those laboratories that are not equipped with facilities for measuring radioactivity.