D-myo-Inositol 1,4,5-trisphosphate tripotassium, a second messenger, elicits Ca 2+ mobilization. D-myo-Inositol 1,4,5-trisphosphate tripotassium inhibits the binding of phosphoinositide-specific phospholipase C-delta 1 (PLC-delta 1) to bilayer membranes composed of phosphatidylcholine (PC) and phosphatidylinositol 4,5-bisphosphate (PIP2).