Effects of Polyamines on Calcium‐Dependent Rat Brain Phosphatidylinositol‐Phosphodiesterase

Abstract

The effect of polyamines on the ability of Ca-dependent soluble rat brain phosphatidylinositol-phosphodiesterase to hydrolyze dispersed phosphatidylinositol was examined. 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 La and Mn. Spermidine partially replaced the Ca requirement of the enzyme. The possibility that polyamines may play a role in the regulation in vivo of phosphatidylinositol-phosphodiesterase is discussed.