D-myo-Inositol-4-phosphate (Ins(4)P1) is a member of the inositol phosphate (InsP) molecular family that play critical roles as small, soluble second messengers in the transmission of cellular signals. The most studied InsP, Ins(1,4,5)P3, is a second messenger produced in cells by phospholipase C (PLC)-mediated hydrolysis of phosphatidylinositol-4,5-diphosphate. 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(4)P1 can be formed by dephosphorylation of Ins(1,4)P2 by inositol polyphosphate 1-phosphatase or dephosphorylated to inositol by inositol monophosphatase.