JBC：新发现的酵素有利于生物质能源原料降解
康乃尔大学(Cornell University)的研究人员发现新的植物酵素，能更有效的将纤维素(cellulose)等制造生质能源的植物原料降解，将比以玉米为原料的生质能源更具经济效益。此研究发表于4月20日的Journal of Biological Chemistry期刊。
Jocelyn Rose教授说：「从富含纤维素的植物来制造乙醇的过程中，最关键的步骤就是如何有效地利用生物转化的过程，将含有大量纤维素的植物细胞壁降解为小分子的糖。目前的技术是使用来自于微生物分泌的酵素cellulases，这个酵素具有一个结构叫作cellulose-binding module (简称为CBM)，能有效的与纤维素结合，然后将纤维素分解成木质纤维素(lignocellulose)，包含本质素(lignin)以及纤维素(cellulose)。而植物中虽然有类似cellulase的酵素，但却不具有CBM的结构，因此，无法有效的将纤维素分解，成为后段生质乙醇制造的瓶颈。」
Jocelyn Rose教授表示：「这个发现于蕃茄中的酵素Endo- -1,4-glucanase，已证明能有效的分解植物细胞壁等物质，有利于生质乙醇的后段制造。研究人员并推敲这个酵素可能是在生长快速的蕃茄中，能有效分解较坚硬的纤维素，由于能将较硬的组织分解，才能使得蕃茄的果实较为松软。而这项发现也有助于生质能源发展的进行。」
（编译/陈瑞娟） (资料来源 : Bio.com)
原始出处:
J. Biol. Chem., Vol. 282, Issue 16, 12066-12074, April 20, 2007
A Tomato Endo-
-1,4-glucanase, SlCel9C1, Represents a Distinct Subclass with a New Family of Carbohydrate Binding Modules (CBM49)*
Breeanna R. Urbanowicz
1, Carmen Catalá, Diana Irwin
, David B. Wilson, Daniel R. Ripoll¶, and Jocelyn K. C. Rose2
From the Departments of Plant Biology and Molecular Biology and Genetics and the ¶Computational Biology Service Unit at the Cornell Theory Center, Cornell University, Ithaca, New York 14853
A critical structural feature of many microbial endo-
-1,4-glucanases (EGases, or cellulases) is a carbohydrate binding module (CBM), which is required for effective crystalline cellulose degradation. However, CBMs are absent from plant EGases that have been biochemically characterized to date, and accordingly, plant EGases are not generally thought to have the capacity to degrade crystalline cellulose. We report the biochemical characterization of a tomato EGase, Solanum lycopersicum Cel8 (SlCel9C1), with a distinct C-terminal noncatalytic module that represents a previously uncharacterized family of CBMs. In vitro binding studies demonstrated that this module indeed binds to crystalline cellulose and can similarly bind as part of a recombinant chimeric fusion protein containing an EGase catalytic domain from the bacterium Thermobifida fusca. Site-directed mutagenesis studies show that tryptophans 559 and 573 play a role in crystalline cellulose binding. The SlCel9C1 CBM, which represents a new CBM family (CBM49), is a defining feature of a new structural subclass (Class C) of plant EGases, with members present throughout the plant kingdom. In addition, the SlCel9C1 catalytic domain was shown to hydrolyze artificial cellulosic polymers, cellulose oligosaccharides, and a variety of plant cell wall polysaccharides.
Received for publication, August 18, 2006 , and in revised form, January 26, 2007.
* This work was supported in part by United States Department of Agriculture NRI Award 2002-35304-12680 (to J. K. C. R. and C. C.) and by grants from the United States National Science Foundation Plant Genome Program (DBI-0606595) and New York State Office of Science, Technology, and Academic Research (NYSTAR). This research was conducted in part with the resources of the Cornell Theory Center, which receives funding from Cornell University, New York State, Federal agencies, foundations, and corporate partners. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The on-line version of this article (available at http://www.jbc.org) contains supplemental Tables S1 and S2.
1 Supported by United States Department of Agriculture Initiative for Future Agricultural and Food Systems Multidisciplinary Graduate Education Traineeship Fellowship 2001-52014-11484.
2 To whom correspondence should be addressed: Dept. of Plant Biology, 228 Plant Science Bldg., Cornell University, Ithaca, NY 14853. Tel.: 607-255-4781; Fax: 607-255-5407; E-mail: jr286@cornell.edu .
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