Modification of polysaccharides and plant cell wall by endo-1,4-b- glucanase and cellulose-binding domains Ilan Levy a , Ziv Shani b , Oded Shoseyov a, * a The Faculty of Agricultural, Food and Environmental Quality Sciences, The Institute of Plant Science and Genetics in Agriculture and The Otto Warburg Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel b CBD-Technologies Ltd., Tamar Science Park, PO Box 199, Rehovot 76100, Israel Received 24 July 2001; received in revised form 11 March 2002; accepted 13 March 2002 Abstract Cellulose is one of the most abundant polymers in nature. Different living systems evolved simultaneously, using structurally similar proteins to synthesize and metabolize polysaccharides. In the growing plant, cell wall loosening, together with cellulose biosynthesis, enables turgor-driven cell expansion. It has been postulated that endo-1,4-b-glucanases (EGases) play a central role in these complex activities. Similarly, microorganisms use a consortium of lytic enzymes to convert cellulose into soluble sugars. Most, if not all, cellulases have a modular structure with two or more separate independent functional domains. Binding to cellulose is mediated by a cellulose-binding domain (CBD), whereas the catalytic domain mediates hydrolysis. Today, EGases and CBDs are known to exist in a wide range of species and it is evident that both possess immense potential in modifying polysaccharide materials in-vivo and in-vitro. The hydrolytic function is utilized for polysaccharide degradation in microbial systems and cell wall biogenesis in plants. The CBDs exerts activity that can be utilized for effective degradation of crystalline cellulose, plant cell wall relaxation, expansion and cell wall biosynthesis. Applications range from modulating the architecture of individual cells to an entire organism. These genes, when expressed under specific promoters and appropriate trafficking signals can be used to alter the nutritional value and texture of agricultural crop and their final products. EGases and CBDs may also find applications in the modification of physical and chemical properties of composite materials to create new materials possessing improved properties. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Cellulose; Cell wall; Cellulose-binding domain (CBD); EGase; Endo-1,4-b-glucanase; Forestry; Pulp; Paper 1. Introduction Plant cell walls are important structures that are specifically designed for a variety of potentially oppos- ing functions. On the one hand, cell walls are responsible for tensile strength, cell shape and resistance to patho- gen invasion. On the other hand, they have to maintain reasonable flexibility against breaking forces and a minimal degree of permeability to allow building blocks and signaling molecules to enter the living cells. There- fore, modifications of living cell walls require a sensitive, highly synchronized system of signals, enzymes and building blocks. It is now well established that living organisms contain complex systems for the management of cellu- lose-containing materials. One of the pivotal players in these systems is endo-1,4-b-glucanase (EGase), which hydrolyzes polysaccharides possessing 1,4-b-glucan. An- other player that appears to be present mainly in systems devoted to cellulose degradation rather than cellulose synthesis is the cellulose-binding domains (CBD). This important, naturally occurring protein entity is contained within many EGases as well as other enzymes. It plays an essential role in the mechanism of cellulose degradation and has the potential to modify cellulose-containing materials. This article reviews the nature and potential applica- tions of EGase and CBD in the modification of polysaccharides and polysaccharide-containing materi- als. * Corresponding author. Tel.:  /972-8-9489084; fax:  /972-8- 9462283 E-mail address: shoseyov@agri.huji.ac.il (O. Shoseyov). Biomolecular Engineering 19 (2002) 17  /30 www.elsevier.com/locate/geneanbioeng 1389-0344/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S1389-0344(02)00007-2