Converts phosphatidylinositol 4,5-bisphosphate (PtdIns 4,5-P2) to PtdIns 5-P. IpgD is injected by Shigella into the host cell and is required for invasion. The accumulation of PtdIns 5-P causes membrane ruffling and actin cytoskeleton rearrangements at the entry site. Acts in concert with IpaA to coordinate and control the membrane and cytoskeletal rearrangements induced early after invasion of the host cell. a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-4,5-bisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-5-phosphate) + phosphate Secreted via the Mxi-Spa type III secretion system. It is stored in the bacterial cytoplasm associated with the chaperone IpgE before being secreted in response to activation of the type III secretion system. By growth at 37 degrees Celsius. Contains the consensus sequence Cys-X(5)-Arg characteristic of Mg-independent phosphatases. Belongs to the phosphatase IpgD/SopB family.