关键词: &beta, -N-乙酰氨基葡萄糖苷酶, 粪肠球菌, 克隆, 表达, 酶学性质

Abstract: N-acetylglucosamine has broad application prospects due to its important functional activity. β-N-acetylglucosaminide is an important glycoside hydrolase in the field of enzymatic preparation of N-acetylglucosamine. A β-N-acetylaminoglycosidase gene from Enterococcus faecalis was cloned and heterologously expressed in Escherichia coli BL21. EfNagase showed the highest sequence similarity with Streptococcus pneumoniae TIGR4 β-N-acetylglucosaminidase (52.08%). The purified recombinant EfNagase displayed its activity on pNP-GlcNAc with specific activity 3 606.10 U/mg. It showed optimal activities at 50℃ and pH 6.0. It exhibited ultra-high stability (residual enzyme activity >90%) at temperatures below 50°C and pH 3.5~11.5. β-N-acetylglucosaminidase is an important class of glycoside hydrolase in the preparation of N-acetylglucosamine by enzymatic method. This study found that EfNagase had high enzymatic activity, high thermostability and strict substrate specificity, which has the potential to be used for the efficient preparation of N-acetylglucosamine.

Key words: β-N-acetylglucosaminidase, Enterococcus faecalis, cloning, expression, characterization