C-terminal domain truncation improves the activity of chitinase derived from Bacillus thuringiensis

Abstract:

[Objective] Using protein domain engineering to construct and optimize the enzymatic activity of chitinase BtChiA derived from Bacillus thuringiensis BMB 171,and constructing qualitative and quantitative analysis of the product of the enzyme hydrolyzing colloidal chitin.[Methods] According to the sequence of BtChiA,the composition of its domain was analyzed.The expression strain of BtChiA and mutant protein with partial domain deletion in Escherichia coli was constructed and then the protein was expressed and purified.Analyzing the type and content of chitinase hydrolysates by HPLC.[Results] BtChiA (full-length protein) and BtChiA△50(truncated chitin binding domain CBD and fibronectin domain FnIII) were obtained by heterologous expression and purification.The vitality of BtChiA△50 to hydrolyze colloidal chitin is 1.64 times higher than that of BtChiA.The hydrolyzed products of both are chitin monosaccharide GlcNAc and chitobiose (GlcNAc)₂.The content of (GlcNAc)₂ is 0.97 times lower than GlcNAc in the product of BtChiA,the content of (GlcNAc)₂is 1.79 times higher than GlcNAc in the product of BtChiA△50.[Conclusion] Protein domain engineering is a feasible strategy to improve the activity of chitinase BtChiA and optimize the composition of the hydrolysates.

Key words:Bacillus thuringiensis;chitinase;protein domain engineering;enzyme vitality