Hydrolyzes the N-acetamido groups of N-acetyl-D-glucosamine residues in chitin to form chitosan and acetate (By similarity). Chitosan is required to anchor melanin to the cell wall, for maintenance of cell wall integrity, and for cytokinesis (By similarity). [(1->4)-N-acetyl-beta-D-glucosaminyl](n) + n H2O = n acetate + chitosan GPI-anchored cell membrane protein (GPI-PMP) (By similarity). Non-covalently associated to the cell wall by means independent of both its GPI-anchor and beta-1,6-glucan (By similarity). Cell membrane localization is critical for effective deacetylase activity (By similarity). Glycosylated. Potential vaccine candidate; elicits T-cell activation when injected in mice. Belongs to the polysaccharide deacetylase family.