Preferentially hydrolyzes pNP-GlcNAc, hydrolyzes pNP-GalNAc to a lesser extent. Hydrolysis of terminal non-reducing N-acetyl-D-hexosamine residues in N-acetyl-beta-D-hexosaminides. Activity is decreased by HgCl(2) and maltose. Activity is stimulated by Na(2)SeO(4), BaCl(2), MgCl(2), chondroitin 6-sulfate and phenylmethylsulfonyl fluoride. Optimum pH is 5.0. Active over a broad range of pH values. Has maximum activity at 45 to 60 degrees Celsius. Inactive at temperatures of 70 degrees Celsius and above. Belongs to the glycosyl hydrolase 18 family. Chitinase class II subfamily.