Catalyzes the deacetylation of 1D-myo-inositol 2-acetamido-2-deoxy-alpha-D-glucopyranoside (GlcNAc-Ins) in the mycothiol biosynthesis pathway. 1D-myo-inositol 2-acetamido-2-deoxy-alpha-D-glucopyranoside + H2O = 1D-myo-inositol 2-amino-2-deoxy-alpha-D-glucopyranoside + acetate Binds 1 zinc ion per subunit. Gradually induced by thiol-oxidant diamide, under (probably indirect) control of SigR. Belongs to the MshB deacetylase family.