Exhibits phosphatidylinositol-phosphate phosphatase activity. Has a preference for phosphatidylinositol 5-phosphate (1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-5-phosphate)) in vitro (PubMed:12878591). May be involved in membrane trafficking by dephosphorylating phosphatidylinositides (PubMed:12878591). a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-5-phosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate 1,2-dioctanoyl-sn-glycero-3-phospho-(1D-myo-inositol-5-phosphate) + H2O = 1,2-dioctanoyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate 1-O-alkyl-2-acyl-sn-glycero-3-phospho-(1'-myo-inositol-5'-phosphate) + H2O = 1-O-alkyl-2-acyl-sn-glycero-3-phospho-1D-myo-inositol + phosphate Phospholipid metabolism. Mutants fail to aggregate to form a multicellular organism under conditions of low cell density. Dictyostelium phosphatidylinositol phosphates (PIPs) are unusual, with the lipid chain joined to the sn-1-position of the glycerol backbone by an ether, rather than ester linkage. The composition of the inositol phospholipids in Dictyostelium is strikingly biased, over 95% of the PI, PIP and PIP2 pools contain the C34:1e structure, with an ether-linked C16:0 chain (palmityl or hexadecyl) in the sn-1 position and an ester-linked C18:1 chain (11-octadecenoyl) in the sn-2 position. Belongs to the protein-tyrosine phosphatase family.