Gene cloning and biochemical analysis of thermostable chitosanase (TCH-2) from Bacillus coagulans CK108

Abstract

The DNA sequence of the thermostable chitosanase TCH-2 gene from Bacillus coagulans CK108 showed a 843-bp open reading frame that encodes a protein of 280 amino acids with a signal peptide corresponding to 32 kDa in size. The deduced amino acid sequence of the chitosanase from Bacillus coagulans CK108 has 61.6%, 48.0%, and 12.6% identities to those from Bacillus ehemensis, Bacillus circulans, and Bacillus subtilis, respectively. C-Terminal homology analysis shows that the enzyme belongs to the Cluster I group. The size of the gene was similar to those from mesophiles of the Cluster I group with regard to higher preference for codons ending in G or C. The recombinant chitosanase was electrophoretically purified to homogeneity by only two steps with column chromatography. The half-life of the enzyme was 40 min at 90°C. The purified protein was also highly stable, retaining above 50% residual activities during treatment with denaturants such as urea (8 M) and guanidine•HCl (4 M) at 37°C for 30 min. The enzyme had a useful reactivity and a high specific activity for producing functional oligosaccharides as well, producing the tetramer as a major product.