Cloning and Characterization of Chitin Deacetylase from Euphausia superba .

Chitin deacetylase (CDA) can catalyze the deacetylation of chitin to produce chitosan. In this study, we identified and characterized a chitin deacetylase gene from Euphausia superba ( EsCDA-9k ), and a soluble recombinant protein chitin deacetylase from Euphausia superba of molecular weight 45 kDa was cloned, expressed, and purified. The full-length cDNA sequence of Es CDA-9k was 1068 bp long and encoded 355 amino acid residues that contained the typical domain structure of carbohydrate esterase family 4. The predicted three-dimensional structure of Es CDA-9k showed a 67.32% homology with Penaeus monodon . Recombinant chitin deacetylase had the highest activity at 40 °C and pH 8.0 in Tris-HCl buffer. The enzyme activity was enhanced by metal ions Co 2+ , Fe 3+ , Ca 2+ , and Na + , while it was inhibited by Zn 2+ , Ba 2+ , Mg 2+ , and EDTA. Molecular simulation of Es CDA-9k was conducted based on sequence alignment and homology modeling. The Es CDA-9k F18G mutant showed a 1.6-fold higher activity than the wild-type enzyme. In summary, this is the first report of the cloning and heterologous expression of the chitin deacetylase gene in Euphausia superba . The characterization and function study of Es CDA-9k will serve as an important reference point for future application.