New Class of Chitosanase from <i>Bacillus amyloliquefaciens</i> for the Generation of Chitooligosaccharides

Abstract

Chitooligosaccharides (COS) generated from either chitin (chitin oligosaccharides) or chitosan (chitosan oligosaccharides) have a wide range of applications in agriculture, medicine, and other fields. Here, we report the characterization of a chitosanase from <i>Bacillus amyloliquefaciens</i> (<i>Bam</i>Csn) and the importance of a tryptophan (Trp), W204, for <i>Bam</i>Csn activity. <i>Bam</i>Csn hydrolyzed the chitosan polymer by an endo mode. It also hydrolyzed chitin oligosaccharides and interestingly exhibited transglycosylation activity on chitotetraose and chitopentaose. Mutation of W204, a nonconserved amino acid in chitosanases, to W204A abolished the hydrolytic activity of <i>Bam</i>Csn, with a change in the structure that resulted in a decreased affinity for the substrate and impaired the catalytic ability. Phylogenetic analysis revealed that <i>Bam</i>Csn could belong to a new class of chitosanases that showed unique properties like transglycosylation, cleavage of chitin oligosaccharides, and the presence of W204 residues, which is important for activity. Chitosanases belonging to the <i>Bam</i>Csn class showed a high potential to generate COS from chitinous substrates.