Regioselective syntheses of new tri- and tetrasaccharides from β-glucobioses by Trichoderma viride β-glucosidase and their structural analyses by NMR spectroscopy

A new beta-glucosidase was partially purified from Trichoderma viride cellulase complex. This beta-glucosidase hydrolyzed beta-(1-->2)-, beta-(1-->3)-, beta-(1-->4)-, and beta-(1-->6)-linked glucobioses and catalyzed a transglycosylation reaction of cellobiose to give regioselectively beta-D-Glc-(1-->6)-beta-D-Glc-(1-->4)-D-Glc (yield: 18.8%) and beta-D-Glc-(1-->6)-beta-D-Glc-(1-->6)-beta-D-Glc-(1-->4)-D-Glc (3.7%). Furthermore, the enzyme converted laminarabiose and gentiobiose into beta-D-Glc-(1-->6)-beta-D-Glc-(1-->3)-D-Glc (15.3%) and beta-D-Glc-(1-->6)-beta-D-Glc-(1-->6)-D-Glc (20.2%), respectively. The structures of the products were determined by H-1 and C-13 NMR spectroscopy. This high regio- and stereoselectivity demonstrated by the enzyme could be applied for oligosaccharide synthesis in general. (C) 1999 Elsevier Science Ltd. All rights reserved.