Specificity of chitosanase from Bacillus pumilus.

Partially (25-35%) N-acetylated chitosan was digested by chitosanase from Bacillus pumilus BN-262, and structures of the products, partially N-acetylated chitooligosaccharides, were analyzed in order to investigate the specificity of the chitosanase. The chitosanase produced glucosamine (GlcN) oligosaccharides abundantly, indicating that the chitosanase splits the beta-1,4-glycosidic linkage of GlcN-GlcN. The chitosanase also produced hetero-oligosaccharides consisting of glucosamine and N-acetyl-D-glucosamine (GlcNAc). Three types of the hetero-oligosaccharides purified by cation-exchange chromatography and HPLC were found to have GlcNAc residue at their reducing end and GlcN residue at their non-reducing end, indicating that the chitosanase can also split the linkage of GlcNAc-GlcN. The determination of the mode of action toward partially N-acetylated chitosan enables a classification of chitosanases according to their specificities and a more precise definition of chitosanases.