Participation of Calcium in the Induction of Phosphodiesterase by Cyclic Adenosine 3′,5′-Monophosphate in Dictyostelium discoideum

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Abstract
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(β-aminoethylether)-N, N, N', N'-tetraacetic acid (EGTA) in 20 mM Tris-HCI buffer, pH 7.5, for 2h, 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.