Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tukuba Central 6, 1-1-1 Higashi, Tukuba, Ibaraki 305-8566, Japan.
Department of Bioengineering, Nagaoka University of Technology, 1603-1, Kamitomioka, Nagaoka, Niigata 940-2188, Japan.
FEBS Lett. 2014 May 2;588(9):1731-8. doi: 10.1016/j.febslet.2014.03.023. Epub 2014 Mar 19.
Unlike endo-dissociative-xyloglucanases, Paenibacillus XEG74 is an endo-processive xyloglucanase that contains four unique tryptophan residues in the negative subsites (W61 and W64) and the positive subsites (W318 and W319), as indicated by three-dimensional homology modelling. Selective replacement of the positive subsite residues with alanine mutations reduced the degree of processive activity and resulted in the more endo-dissociative-activity. The results showed that W318 and W319, which are found in the positive subsites, are essential for processive degradation and are responsible for maintaining binding interactions with xyloglucan polysaccharide through a stacking effect.
不同于内-解木聚葡聚糖酶，巨大芽孢杆菌 XEG74 是一种内切型木葡聚糖酶，其在负性亚位点（W61 和 W64）和正性亚位点（W318 和 W319）含有四个独特的色氨酸残基，这通过三维同源建模表明。通过选择性替换正性亚位点残基的丙氨酸突变，降低了内切活性的程度，并导致更内切-解木聚葡聚糖酶活性。结果表明，正性亚位点的 W318 和 W319 对于连续降解是必需的，并且负责通过堆积效应维持与木葡聚糖多糖的结合相互作用。
