Effects of polyamines on calcium-dependent rat brain phosphatidylinositol-phosphodiesterase

The effect of polyamines on the ability of calcium-dependent soluble rat brain phosphatidylinositol-phosphodiesterase to hydrolyze dispersed phosphatidylinositol was examined. Putrescine and cadaverine stimulated activity at all concentrations tested. In contrast, spermine and spermidine stimulated the reaction slightly at low concentrations but caused progressively greater inhibition as their levels were further increased. Phosphatidylinositol hydrolysis was inhibited by several multivalent cations, especially lanthanum and manganese. Spermidine partially replaced the calcium requirement of the enzyme. The possibility that polyamines may play a role in the regulation in vivo of phosphatidylinositol-phosphodiesterase is discussed.