关键词: 环糊精葡萄糖基转移酶；定点突变；环糊精；产物特异性

Abstract: The cyclodextrin glucosyltransferase (CGTase) from the marine Bacillus sp. Y112 was analyzed by homologous modeling and amino acid sequence alignment; it was found that the arginine residue at position 81 from the N-terminus may affect the product specificity. In this study, when this residue was mutated to threonine by site-directed mutagenesis, the yield of α-CD was decreased, and the percentage of β-CD in the cyclization products was increased from 64% to 71%, suggesting the improved product specificity. The underlying reason may be related to the size of the substituted amino acid residue and change in hydrogen bonding interaction. At the same time, the enzymatic properties of the mutant retained the thermophilicity, thermostability, and alkali resistance of the wild-type enzyme.

Key words: cyclodextrin glycosyltransferases; site-directed mutagenesis; cyclodextrin; product speci?city