Characteristics of the Induction of Phosphodiesterases by Cyclic Adenosine 3', 5'-Monophosphate in the Slime Mold, Dictyostelium discoideum

Cyclic adenosine 3', 5'-monophosphate (cAMP) stimulated the induction of cAMP-phosphodiesterases of the slime mold, Dictyostelium discoideum. The membrane phosphodiesterase was induced by more than 10-5 M of cAMP concentration, while the extracellular enzyme was done 3.5-times higher by 10-6 M of cAMP compared with free cAMP. The induction of the extracellular phosphodiesterase by cAMP was inhibited by EDTA, p-chloromercuribenzene sulfonate (PCMB), concanavalin A (Con A) and progesterone which all are known to cease differentiation of the slime mold. The derivation of the extracellular enzyme was also stopped by dithiothreitol which reversely accelerates development of the cells. On the other hand, Con A and dithiothreitol further stimulated the induction of the membrane phosphodiesterase by cAMP more than by cyclic nucleotide alone. Cyclic guanosine 3', 5'-monophosphate and N6, O2'-dibutyryl cyclic adenosine 3', 5'-monophosphate are known to have much less chemotaxis-characteristics of the slime mold than cAMP. These cAMP-analogs occurred the synthesises of both the membrane and the extracellular phosphodiesterases to same or more extent. When the surface of the slime mold was treated with trypsin, the induction of only extracellular phosphodiesterase by cAMP was suppressed to half. From these results, it seems that the induction of synthesis of phosphodiesterases by cAMP in the slime mold is independent of the occurrence of chemotaxis