Structure and Functions of Polysaccharide-degrading Enzyme with High Activity under Extreme Environments

-1,4-木聚糖是具有-1,4-连接木吡喃糖单元的主干的多相多糖。木聚糖酶催化木聚糖水解成低聚木糖和木糖。最近，首席研究员从土壤中分离出嗜碱芽孢杆菌菌株41M-1。菌株41M-1分泌一种新型碱性木聚糖酶，其碱性pH最适。本研究的目的是阐明木聚糖在碱性条件下水解的机制，并设计酶分子以获得更多的嗜极性，如嗜碱性。首席研究员克隆了菌株41M-1的木聚糖酶基因并进行了测序。推导出的氨基酸序列表明，木聚糖酶由n端催化结构域和c端额外的功能未知多肽区域组成。催化区域的Glu-93和Glu-183以及Trp-18、Trp-86、tyrr -84和tyrr -95参与了催化作用。此外，木聚糖酶的c端区域被证明是多糖结合域。

beta-1,4-Xylans are heterogeneous polysaccharides that have a backbone of beta-1,4-linked xylopyranose units. Xylanases catalyze the hydrolysis of xylan to xylooligosaccharides and xylose. Recently, The head investigator has isolated alkaliphilic Bacillus sp.strain 41M-1 from soil. Strain 41M-1 secreted a novel alkaline xylanase that had an alkaline pH optimum. The objective of this study is to elucidate the mechanism of xylan hydrolysis in alkaline conditions and to engineer the enzyme molecules for more extremophilic properties, such as alkaliphily. The head investigator cloned and sequenced the xylanase gene from strain 41M-1. The deduced amino acid sequence revealed that the xylanase consisted of an N-terminal catalytic domain and an additional functionally-unknown polypeptide region at the C-terminus. Glu-93 and Glu-183 in the catalytic domain, as well as Trp-18, Trp-86, Tyr-84 and Tyr-95, were involved in catalysis. Furthermore, the C-terminal region of the xylanase proved to be a polysaccharide-binding domain.