Differences and Similarities Between Guanosine 3′,5′-Cyclic Monophosphate Phosphodiesterase and Adenosine 3′,5′-Cyclic Monophosphate Phosphodiesterase Activities in Neuroblastoma Cells in Culture

Abstract

Summary

There are phosphodiesterase activities in both particulate and supernatant fractions which hydrolyze guanosine 3′,5′-cyclic monophosphate (cGMP) and adeno-sine 3′,5′-cyclic monophosphate (cAMP) with an apparent K_m of 2-8 μM and with an apparent K_m of 44-222 μM. 4-(3-Butoxy-4-methoxybenzyl-2-imidazolidinone (R020-1724) did not inhibit cGMP phosphodies-terase activity in homogenates of mouse neuroblastoma cells, but markedly inhibited cAMP phosphodiesterase activity. Papaver-ine and theophylline inhibited both cGMP and cAMP phosphodiesterase activities to about the same extent. The former was more potent than the latter. The specific activity of cGMP phosphodiesterase as a function of protein concentrations first increased and then decreased. The specific activity of cAMP phosphodiesterase decreased under a similar experimental condition.