Rat brain and liver soluble phospholipase C: resolution of two forms with different requirements for calcium.

Two forms of phospholipase C, hydrolyzing specifically inositol phospholipids, are resoluted and partially purified from rat brain as well as liver cytosol by DEAE-cellulose followed by heparin-Sepharose, Sephacryl S-400, and aminohexyl-Sepharose column chromatographies. With phosphatidylinositol as substrate, at pH 7.4 one is most active at 10(-6) M Ca2+ (Type I) whereas the other requires 10(-3) M Ca2+ (Type II). At pH 5.5 both Type I and II are active at 10(-3) M Ca2+ but essentially inactive at lower concentrations of this divalent cation. Both Type I and II hydrolyze preferentially polyphosphoinositides particularly at lower concentrations of Ca2+.