Structural evidence for the evolution of xyloglucanase activity from xyloglucan endo-transglycosylases:: Biological implications for cell wall metabolism
Structural evidence for the evolution of xyloglucanase activity from xyloglucan endo-transglycosylases:: Biological implications for cell wall metabolism
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DOI：
10.1105/tpc.107.051391
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发表时间：
2007-06-01
期刊：
影响因子：
11.6
通讯作者：
Brumer, Harry, III
中科院分区：
文献类型：
--
作者：
Baumann, Martin J.;Eklof, Jens M.;Brumer, Harry, III
高分辨率，三维结构的原型糖苷水解酶家族16（GH 16）内切木葡聚糖酶Tm-NXG 1和Tm-NXG 2从旱金莲（金莲花）已经解决了x射线晶体学。通过重组表达酶的结构-功能研究，并与来自杂交白杨（美洲山杨3号美洲山杨）的严格木葡聚糖内切转糖基酶Ptt-XET 16 -34的数据进行比较，确定了调节GH 16木葡聚糖活性酶中底物水解转糖基化相对速率的关键结构特征。环缺失变体Tm-NXG 1-Delta YNIIG的产生产生了结构上类似于Ptt-XET 16 -34的酶，并且具有大大增加的转糖基化：水解比率。全面的XTH基因产物的生物信息学分析，连同详细的动力学数据，强烈表明，木葡聚糖酶活性已演变为在祖先GH 16 XET的功能增益，以满足特定的生物学要求在种子萌发，果实成熟，和快速壁扩张。
High-resolution, three-dimensional structures of the archetypal glycoside hydrolase family 16 (GH16) endo-xyloglucanases Tm-NXG1 and Tm-NXG2 from nasturtium (Tropaeolum majus) have been solved by x-ray crystallography. Key structural features that modulate the relative rates of substrate hydrolysis to transglycosylation in the GH16 xyloglucan-active enzymes were identified by structure-function studies of the recombinantly expressed enzymes in comparison with data for the strict xyloglucan endo-transglycosylase Ptt-XET16-34 from hybrid aspen ( Populus tremula 3 Populus tremuloides). Production of the loop deletion variant Tm-NXG1-Delta YNIIG yielded an enzyme that was structurally similar to Ptt- XET16-34 and had a greatly increased transglycosylation: hydrolysis ratio. Comprehensive bioinformatic analyses of XTH gene products, together with detailed kinetic data, strongly suggest that xyloglucanase activity has evolved as a gain of function in an ancestral GH16 XET to meet specific biological requirements during seed germination, fruit ripening, and rapid wall expansion.