IPPase; Inositol polyphosphate-1-phosphatase, a member of the Mg++ dependent family of inositol monophosphatase-like domains, hydrolyzes the 1' position phosphate from inositol 1,3,4-trisphosphate and inositol 1,4-bisphosphate. Members in this group may also exhibit 3'-phosphoadenosine 5'-phosphate phosphatase activity, and they all appear to be inhibited by lithium. IPPase is one of the proposed targets of Li+ therapy in manic-depressive illness.