关键词: 嗜热酸性生淀粉α-淀粉酶, 环化重排, 生淀粉吸附率, 生淀粉降解率, 催化性能

Abstract: In order to determine the effect of domain C of thermoacidiphilic raw starch-degrading α-amylase Gt-amy on its catalytic properties, circulation permutation based on protein molecular structure was used to construct circularly permutated mutants of Gt-amy. The abilities of Gt-amy and the mutants to adsorb onto and hydrolyze raw corn starch were investigated. Moreover, the specific activities and kinetic constants were also measured. Compared with Gt-amy, the mutants with higher raw corn starch-binding capacity had higher raw corn starch degradation capacity, and those with lower raw corn starch binding capacity had lower raw corn starch degradation capacity, i.e, there was a positive correlation between Gt-amy’s capacity to bind to and degrade raw corn starch. The raw corn starch binding and degradation rates of mutant Gt-amy-S498 were 93.14% and 90.93%, respectively, which were higher than those of Gt-amy (78.86% and 65.80%). This study confirms that circulation permutation can be used as an engineering method to change the structure and function of proteins, and provides a new way to improve the catalytic performance of enzymes.

Key words: thermoacidiphilic raw starch degrading α-amylase, circulation permutation, raw starch binding, raw starch hydrolysis, catalytic performance