Specific amino acids responsible for the cold adaptedness of Micrococcus antarcticus beta-glucosidase BglU----中国科学院微生物研究所

科研成果

论文题目:	Specific amino acids responsible for the cold adaptedness of Micrococcus antarcticus beta-glucosidase BglU
作者:	Miao, Li-Li Fan, Hong-Xia Qu, Jie Liu, Ying Liu, Zhi-Pei
联系作者:	Liu, Zhi-Pei*
刊物名称:	Appl Microbiol Biotechnol
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年份:	2016
影响因子:	3.882
论文下载:	http://link.springer.com/article/10.1007%2Fs00253-016-7990-x
摘要:	Psychrophilic enzymes display efficient activity at moderate or low temperatures (4-25 degrees C) and are therefore of great interest in biotechnological industries. We previously examined the crystal structure of BglU, a psychrophilic beta-glucosidase from the bacterium Micrococcus antarcticus, at 2.2 A resolution. In structural comparison and sequence alignment with mesophilic (BglB) and thermophilic (GlyTn) counterpart enzymes, BglU showed much lower contents of Pro residue and of charged amino acids (particularly positively charged) on the accessible surface area. In the present study, we investigated the roles of specific amino acid residues in the cold adaptedness of BglU. Mutagenesis assays showed that the mutations G261R and Q448P increased optimal temperature (from 25 to 40-45 degrees C) at the expense of low-temperature activity, but had no notable effects on maximal activity or heat lability. Mutations A368P, T383P, and A389E significantly increased optimal temperature (from 25 to 35-40 degrees C) and maximal activity (~1.5-fold relative to BglU). Thermostability of A368P and A389E increased slightly at 30 degrees C. Mutations K163P, N228P, and H301A greatly reduced enzymatic activity-almost completely in the case of H301A. Low contents of Pro, Arg, and Glu are important factors contributing to BglU's psychrophilic properties. Our findings will be useful in structure-based engineering of psychrophilic enzymes and in production of mutants suitable for a variety of industrial processes (e.g., food production, sewage treatment) at cold or moderate temperatures.