Hydrolyzes chitosan and chitooligosaccharides with retention of anomeric configuration. Has maximum activity on chitotetraose, chitopentaose and their corresponding alcohols, with a slight decrease in the rate of hydrolysis on longer chains. Has no activity against beta-D-glucopyranoside, beta-D-xylopyranoside, beta-D-mannoside, beta-D-glucuronide, beta-D-galactoside, beta-D-N-acetylgalactosamide, beta-D-N-acetylglucosaminide and alpha-D-N-acetylglucosaminide. Hydrolysis of chitosan or chitosan oligosaccharides to remove successive D-glucosamine residues from the non-reducing termini. Optimum pH is 5.5 with chitotriitol as substrate, and 5.3 with (GlcN)2 as substrate. Activity is lost below pH 3.5 and above pH 8.0. Optimum temperature is 60 degrees Celsius. Stable below 50 degrees Celsius, inactive above 60 degrees Celsius. Monomer. Belongs to the glycosyl hydrolase 2 family.