Hydrolyzes chitosan and chitooligosaccharides with retention of anomeric configuration. Has no activity against beta-D-galactoside, beta-D-glucuronide, beta-D-mannoside, chitin, glycol chitosan, cellulose, N,N'-diacetylchitibiose and pNP-GlcNAc (By similarity). Hydrolysis of chitosan or chitosan oligosaccharides to remove successive D-glucosamine residues from the non-reducing termini. Monomer. Belongs to the glycosyl hydrolase 2 family.