Catalyzes the dephosphorylation of inositol 1-phosphate (I-1-P) to yield free myo-inositol, a key metabolite in mycobacteria. Is also able to hydrolyze a variety of polyol phosphates such as glucitol-6-phosphate, inositol 2-phosphate (I-2-P), glycerol-2-phosphate, and 2'-AMP, albeit with reduced efficiency. a myo-inositol phosphate + H2O = myo-inositol + phosphate Magnesium. Co(2+) and Fe(2+) can replace Mg(2+) but lead to a partial activity (30%), and Mn(2+) leads to a partial activity of 13%. Inhibited by Li(+) with IC50 value of 0.9 mM but not by Na(+) or K(+). Also inhibited by Zn(2+) (IC50 value of 0.5 uM) and by concentrations of Mg(2+) higher than 100 mM. Optimum pH is 8.5. Exhibits a dramatic drop in activity at low pH, with less than 50% activity remaining at pH 7. In contrast, the activity is extremely stable at alkaline pH, with more than 50% activity remaining at pH 12. Optimum temperature is 80 degrees Celsius. Loses 80% activity after a 2 minutes incubation at 70 degrees Celsius. Polyol metabolism; myo-inositol biosynthesis; myo-inositol from D-glucose 6-phosphate: step 2/2. Homodimer. Dimerization is induced by Mg(2+) binding. When comparing gene expression levels of the four IMPase family genes in exponential cultures of M.tuberculosis, the level of cysQ is the highest, almost equal to sigA; impA and impC are expressed at approximately 40% of this level, while suhB is lowest, at 12% of the cysQ level. Strains lacking this gene show no difference in colony morphology and no differences in levels of phosphatidylinosotol mannosides (PIMs), lipomannan (LM), lipoarabinomannan (LAM) or mycothiol (in the absence of exogenous inositol). Belongs to the inositol monophosphatase superfamily.