Ins(3)P1 is a member of the inositol phosphate (InsP) molecular family of second messengers that play a critical role in the transmission of cellular signals. The most studied InsP, Ins(1,4,5)P3, is a second messenger produced in cells by PLC-mediated hydrolysis of phosphatidylinositol-4,5-biphosphate. Binding of Ins(1,4,5)P3 to its receptor on the endoplasmic reticulum results in opening of the calcium channels and an increase in intracellular calcium. Ins(3)P1 can be formed by the dephosphorylation of polyphosphate inositols such as Ins(3,4)P2 by inositol polyphosphate 4-phosphatase.