X-ray crystallographic studies of family 11 xylanase Michaelis and product complexes: Implications for the catalytic mechanism

WanQ.; ZhangQ.; Hamilton-BrehmS.WeissK.MustyakimovM.CoatesL.LanganP.GrahamD.KovalevskyA.

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X-ray crystallographic studies of family 11 xylanase Michaelis and product complexes: Implications for the catalytic mechanism

机译：x射线晶体研究家庭11木聚糖酶米歇利斯和产品复合物:对催化机理的影响

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Xylanases catalyze the hydrolysis of plant hemicellulose xylan into oligosaccharides by cleaving the main-chain glycosidic linkages connecting xylose subunits. To study ligand binding and to understand how the pH constrains the activity of the enzyme, variants of the Trichoderma reesei xylanase were designed to either abolish its activity (E177Q) or to change its pH optimum (N44H). An E177Q-xylohexaose complex structure was obtained at 1.15 ? resolution which represents a pseudo-Michaelis complex and confirmed the conformational movement of the thumb region owing to ligand binding. Co-crystallization of N44H with xylohexaose resulted in a hydrolyzed xylotriose bound in the active site. Co-crystallization of the wild-type enzyme with xylopentaose trapped an aglycone xylotriose and a transglycosylated glycone product. Replacing amino acids near Glu177 decreased the xylanase activity but increased the relative activity at alkaline pH. The substrate distortion in the E177Q-xylohexaose structure expands the possible conformational itinerary of this xylose ring during the enzyme-catalyzed xylan-hydrolysis reaction.

机译：木聚糖酶催化的水解植物半纤维素木聚糖为低聚糖裂开的主链糖苷的联系连接木糖的子单元。绑定和了解pH值限制酶的活性的变体木霉属reesei木聚糖酶的设计要么取消其活动(E177Q)或改变它的最佳pH值(N44H)。复杂结构在1.15了吗?代表一个pseudo-Michaelis决议复杂的构象运动和确认拇指地区由于配体绑定。Co-crystallization N44H xylohexaose导致水解xylotriose绑定的活跃的站点。酶与xylopentaose困糖苷配基xylotriose和transglycosylated glycone产品。降低了木聚糖酶的活动,但增加了相对活动碱性博士衬底E177Q-xylohexaose结构扭曲扩展的构象行程这在酶催化木糖环xylan-hydrolysis反应。

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《Acta crystallographica.Section D Biological crystallography.》 |2014年第1期|11-23|共13页
作者
WanQ.; ZhangQ.; Hamilton-BrehmS.WeissK.MustyakimovM.CoatesL.LanganP.GrahamD.KovalevskyA.;
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Biosciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831, United States;

Biology and Soft Matter Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831;

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正文语种英语
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关键词
Trichoderma reesei; Glycoside Hydrolases; Mutagenesisglycosidic linkagesLigand Bindingenzyme variantXylan Endo-1,3-beta-Xylosidasexylotriose;

机译：Bindingenzyme variantXylanEndo-1, 3-beta-Xylosidasexylotriose;

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X-ray crystallographic studies of family 11 xylanase Michaelis and product complexes: Implications for the catalytic mechanism

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