In vitro PKA phosphorylation-mediated human PDE4A4 activation

The PDE4 catalytic machinery comprises, in part, two divalent cations in a binuclear motif Here we report that PDE4A4 expressed in Sf9 cells exhibits a biphasic Mg2+ dose-response (EC50 of similar to 0.15 and > 10 mM) in catalyzing cAMP hydrolysis. In vitro phosphorylation of PDE4A4 by the PKA-catalytic subunit increases the enzyme's sensitivity to Mg2+, leading to 4-fold increased cAMP hydrolysis without affecting its K-m. The phosphorylation also increases the potencies of (R)- and (S)-rolipram without affecting CDP-840 and SB-207499. The results support that modulating the cofactor binding affinity of PDE4 represents a mechanism for regulating its activity. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.