Arabidopsis 2010: Collaborative Project on the Functional Genomics of Arabidopsis beta-Glucosidase and beta-Galactosidase Gene Families

O-糖苷水解酶（EC 3.2.1.-）广泛存在于动物、植物和微生物中，是催化两种或多种碳水化合物之间或碳水化合物和非碳水化合物部分之间的化学键断裂的酶。为了应对2010年计划的挑战，即在未来十年内确定所有拟南芥基因的功能，这项合作研究将集中在两个相关糖苷水解酶家族的大约75个成员（http：www.biol.vt.edu/faculty/esen/glycosidase.lab.html和http：//afmb.cnrs-mrs.fr/campedro/CAZY/）。家族1包括β-葡糖苷酶（EC 3.2.1.21）和黑芥子酶（EC 3.2.3.1），它们在高等植物中对食草动物和病原体的化学防御、木质素生物合成以及植物生长和发育中起作用。家族35包含β-半乳糖苷酶（EC 3.2.1.23），其在果实成熟、花衰老、碳水化合物储备的动员和半乳糖脂周转中起关键作用。迄今为止，只有三个这些拟南芥水解酶的确切的生化作用是已知的肯定。这项多学科合作研究的目的是为拟南芥基因组编码的β-葡萄糖苷酶和β-半乳糖苷酶分配生物学功能。在使用系统发育分析鉴定含有密切相关的酶的亚家族后，将获得编码每种靶水解酶的cDNA。然后将每种水解酶在外源宿主（例如酵母和细菌）细胞中过表达，并纯化以通过测量其对广泛的天然糖苷底物的酶活性来确定其生物学功能，所述天然糖苷底物主要从拟南芥和相关十字花科植物分离用于此目的。在平行的研究中，选定的亚家族代表的三维结构将通过同源建模和X-射线衍射来确定，为这些水解酶如何识别和结合其底物提供新的见解。这一信息将是至关重要的，在未来的研究，以改变家庭1和家庭35水解酶的底物特异性的生物技术的目的，包括生物质转化和改善抗草食动物防御和果实成熟。

Widely distributed in animals, plants and microbes, O-glycoside hydrolases (EC 3.2.1.-) are enzymes that catalyze the cleavage of chemical bonds between two or more carbohydrates or between a carbohydrate and a non-carbohydrate moiety. Responding to the challenge of the 2010 Project to identify the function of all Arabidopsis thaliana genes within the next decade, this collaborative research will focus on approximately 75 members of two related families of glycoside hydrolases (http://www.biol.vt.edu/faculty/esen/glycosidase.lab.html and http://afmb.cnrs-mrs.fr/~pedro/CAZY/). Family 1 includes beta -glucosidases (EC 3.2.1.21) and myrosinases (EC 3.2.3.1), which function in higher plants in chemical defense against herbivores and pathogens, lignin biosynthesis, and plant growth and development. Family 35 contains the beta -galactosidases (EC 3.2.1.23), which play key roles in fruit ripening, flower senescence, mobilization of carbohydrate reserves, and galactolipid turnover. To date, the precise biochemical roles of only three of these Arabidopsis hydrolases are known with certainty. The purpose of this multidisciplinary collaborative research is to assign biological functions to beta-glucosidases and beta-galactosidases encoded by the Arabidopsis genome. After using phylogenetic analysis to identify subfamilies that contain closely related enzymes, cDNAs encoding each target hydrolase will be obtained. Each hydrolase will then be overexpressed in foreign host (e.g. yeast and bacteria) cells and purified to ascertain its biological function by measuring its enzymatic activity toward a wide range of natural glycosidic substrates isolated primarily from Arabidopsis and related crucifers for this purpose. In parallel studies, three-dimensional structures of selected subfamily representatives will be determined by homology modeling and x-ray diffraction, providing novel insights into how these hydrolases recognize and bind their substrates. This information will be of paramount importance in future research to alter the substrate specificity of Family 1 and Family 35 hydrolases for biotechnological purposes, including biomass conversion and improvements in anti-herbivore defenses and fruit ripening.