Regulation of the high Km cyclic nucleotide phosphodiesterase of adrenal medulla by the endogenous calcium-dependent-protein activator.

Abstract A cyclic nucleotide phosphodiesterase sensitive to the calcium-dependent endogenous protein activator has been identified in rat and beef adrenal medulla. In this tissue the ratio between the activity of this enzyme and that of the low Km enzyme is smaller than the corresponding ratio in rat brain. The activator-sensitive phosphodiesterase, isolated from beef adrenal medulla has a high Km for cyclic 3,5-AMP. Saturating concentrations of the calcium dependent protein activator decreased significantly the apparent Km of this enzyme using cAMP as a substrate.