Participation of calcium in the induction of phosphodiesterase by cyclic adenosine 3',5'-monophosphate in Dictyostelium discoideum.

The effects of divalent cations on the induction of phosphodiesterase [EC 3.1.4.17] by cyclic adenosine 3',5'-monophosphate (cyclic AMP) were studied in Dictyostelium discoideum. When cells were incubated with 1 mM ethylene glycol-bis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) in 20 mM Tris-HCl buffer, pH 7.5, for 2 h, the induction of cellular phosphodiesterase was inhibited by about 80%, and that of extracellular phosphodiesterase by about 65%. When cells were incubated with 1 mM EGTA for 1 h, 2 mM CaCl2 was added and the cells were further incubated for 1 h, the activities of cellular and extracellular phosphodiesterases were increased about 5 and 2.5 times, respectively, compared with those in the EGTA-inhibited cells. Although various other kinds of divalent cations were also studied, Ca2+ had the greatest effect on the induction. These results suggest that Ca2+ may participate in the induction of phosphodiesterase, and thus in the regulation of the development of the cellular slime mold.