Structural analyses of new tri- and tetrasaccharides produced from disaccharides by transglycosylation of purified Trichoderma viride b-glucosidase Hiroyuki Kono*, Shin Kawano, Kenji Tajima, Tomoki Erata and Mitsuko Takai Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628 Japan A new b-glucosidase was partially purified from Trichoderma viride cellulase. This b-glucosidase catalyzed a transglycosy- lation reaction of cellobiose to give b-D-Glc-(1→6)-b-D-Glc-(1→4)-D-Glc (1, yield: 18.8%) and b-D-Glc-(1→6)-b-D-Glc-(1→6)-b-D- Glc-(1→4)-D-Glc (2, 3.7%), regioselectively. Furthermore, the enzyme regioselectively converted laminaribiose and gentiobiose into b-D-Glc-(1→6)-b-D-Glc-(1→3)-D-Glc (3, 15.3%) and b-D-Glc-(1→6)-b-D-Glc-(1→6)-D-Glc (4, 20.2%), respectively. The structures (1–4) of the products were determined by 1 H and 13 C NMR spectroscopies. This high regio- and stereoselec- tively of the b-glucosidase could be applied for oligosaccharide synthesis. Keywords: Trichoderma viride, b-glucosidase, transglycosylation, two-dimensional NMR spectroscopy, oligosaccharide synthesis Introduction Cellulase is generally characterized by three components [1,2]: endoglucanase [EC 3.2.1.4], exo-glucan cellobiohy- drolase [EC 3.2.1.91], and b-glucosidase [EC 3.2.1.21]. Of these enzymes, endoglucanase and exo-glucan cellobiohy- drolase act synergistically to hydrolyze crystalline cellu- lose to form cellooligosaccharides, while b-glucosidase hydrolyzes the cellooligosaccharide to glucose [1,2]. Some b-glucosidases are known to catalyze hydrolysis and trans- glycosylation [3–7]. Although the physiological signifi- cance of the latter reaction is not clear, it is believed to play a important role in the production of cellulase in- ducers [1]. Thus, clarification of the mechanism of the transglycosylation by b-glucosidase is important to eluci- date the biological function of the b-glucosidase in the cellulase-producing microorganisms. Recently, with increasing interest in oligosaccharide components of glycoproteins and glycolipids, b-glucosi- Glycoconjugate Journal 16, 415–423 (1999) © 2000 Kluwer Academic Publishers. Manufactured in The Netherlands *To whom correspondence should be addressed. Tel / Fax: +81-11-706- 6568; E-mail: kohno@dove-mc.eng.hokudai.ac.jp