Catalysis of the reaction: 1D-myo-inositol 2-acetamido-2-deoxy-alpha-D-glucopyranoside + H2O = 1D-myo-inositol 2-amino-2-deoxy-alpha-D-glucopyranoside + acetate. This reaction is the hydrolysis of an acetyl group from N-acetylglucosaminylinositol.