[protein]-C-terminal carboxyl phosphoethanolamide-(1-radyl-2-octadecanoyl)-GPI(deacylinositol-H7) + H2O = [protein]-C-terminal carboxyl phosphoethanolamide-glycosylinositol-1-phosphate (deacylinositol-H7) + 1-radyl-2-octadecanoyl-sn-glycerol + H(+) — reaction