The hydrolysis of triphosphoinositide by a phosphodiesterase in rat kidney cortex

The hydrolysis of triphosphoinositide by a phosphodiesterase has been demonstrated in rat kidney cortex. Subcellular fractionation studies revealed that the enzyme activity was predominantly found in the supernatant fraction. After acid precipitation and ammonium sulfate fractionation, the soluble enzyme was free from triphosphoinositide phosphomonoesterase activity.Although the partially purified enzyme did not require added divalent cations for activity, it was strongly inhibited by EDTA (0.1 mm). In the absence of EDTA, added MgCl₂ or CaCl₂ depressed the enzyme activity. The enzyme preparation was specific to polyphosphoinositides; it did not attack phosphatidylinositol and other phospholipids. It hydrolyzed both diphosphoinositide and triphosphoinositide with the formation of 1,2-diglyceride and organic phosphate.