Catalyzes the dephosphorylation of inositol 1-phosphate (I-1-P) to yield free myo-inositol, a key metabolite in mycobacteria. a myo-inositol phosphate + H2O = myo-inositol + phosphate Polyol metabolism; myo-inositol biosynthesis; myo-inositol from D-glucose 6-phosphate: step 2/2. Inactivation of this gene results in an altered colony morphology, reduced levels of PI dimannoside (PIM2), and altered permeability of the cell wall. Belongs to the inositol monophosphatase superfamily.