Regulation of cyclic 3',5'-adenosine monophosphate phosphodiesterase in Friend erythroleukemia cells.

Friend erythroleukemia cells contain only a single form of cAMP phosphodiesterase with high affinity for substrate. It is activated by treatment with various proteases including those present in snake venom. The activity of this enzyme is increased about 2-fold when the cells are either cultivated in the presence of cAMP or in the presence of compounds which are capable of generating cAMP in vivo, such as isoproterenol, epinephrine and prostaglandins. The enzyme produced in the presence of cAMP is modified in such a way that it is no longer susceptible to activation by treatment with proteases. The activation and modification obtained in vivo can be duplicated in cell-free extracts of Friend cells, if they are incubated in the presence of cAMP and ATP. A possibility thus exists that the phosphodiesterase is activated by its substrate by phosphorylation.