腸道中的細(xì)菌如何打破糖的復(fù)雜結(jié)構(gòu)？在1月在線出版的《自然—化學(xué)生物學(xué)》期刊上,，研究人員發(fā)表了他們的新觀點(diǎn),，新成果將有助于人類(lèi)飲食結(jié)構(gòu)的配搭。
在生長(zhǎng)的過(guò)程中,，細(xì)菌需要以糖作為食物,。腸中的細(xì)菌也被稱(chēng)為“共生菌”，它們通過(guò)打破糖 的大鏈接或復(fù)合糖的結(jié)構(gòu)來(lái)獲取糖,，這些糖源自人類(lèi)的飲食和細(xì)胞,，糖的分解過(guò)程對(duì)人類(lèi)的健康和消化過(guò)程來(lái)說(shuō)至關(guān)重要。然而,，在這一過(guò)程中執(zhí)行這些任務(wù)的特定蛋白質(zhì)卻一直讓人難以捉摸,。特別的是，一種非常普通的糖復(fù)合體也含有4種不同的化學(xué)鍵,，需要4種糖苷水解酶來(lái)打破這些鍵接,。
現(xiàn)在，Harry Gilbert和Gideon Davies與同事合作,，在人體腸菌中發(fā)現(xiàn)的23個(gè)糖苷水解酶中,，描述了其中22個(gè)的特征,。出人意料的是，他們發(fā)現(xiàn)了大范圍的酶功能,，解釋了這些糖苷水解 酶降解復(fù)雜的糖結(jié)構(gòu)的原理。新發(fā)現(xiàn)增加了我們對(duì)自身體內(nèi)的共生菌和復(fù)雜消化系統(tǒng)的認(rèn)識(shí),。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature Chemical Biology 27 December 2009 | doi:10.1038/nchembio.278
Mechanistic insights into a Ca2+-dependent family of α-mannosidases in a human gut symbiont
Yanping Zhu1,2,7, Michael D L Suits3,7, Andrew J Thompson3, Sambhaji Chavan4, Zoran Dinev5, Claire Dumon1,6, Nicola Smith1, Kelley W Moremen2, Yong Xiang2, Aloysius Siriwardena4, Spencer J Williams5, Harry J Gilbert1,2 & Gideon J Davies3
Colonic bacteria, exemplified by Bacteroides thetaiotaomicron, play a key role in maintaining human health by harnessing large families of glycoside hydrolases (GHs) to exploit dietary polysaccharides and host glycans as nutrients. Such GH family expansion is exemplified by the 23 family GH92 glycosidases encoded by the B. thetaiotaomicron genome. Here we show that these are α-mannosidases that act via a single displacement mechanism to utilize host N-glycans. The three-dimensional structure of two GH92 mannosidases defines a family of two-domain proteins in which the catalytic center is located at the domain interface, providing acid (glutamate) and base (aspartate) assistance to hydrolysis in a Ca2+-dependent manner. The three-dimensional structures of the GH92s in complex with inhibitors provide insight into the specificity, mechanism and conformational itinerary of catalysis. Ca2+ plays a key catalytic role in helping distort the mannoside away from its ground-state 4C1 chair conformation toward the transition state.
Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, UK.
Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA.
York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, UK.
Université de Picardie Jules Vernes, Faculté des Sciences, Laboratoire des Glucides, Centre National de la Recherche Scientifique-Unité Mixe de Recherche 6219, Amiens, France.
School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia.
Present address: INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse; Université de Toulouse; INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse; CNRS, UMR5504, F-31400 Toulouse, France.
These authors contributed equally to this work.
