Acceptor specificity of cellobiose phosphorylase from Cellvibrio gilvus: synthesis of three branched trisaccharides.

Cellobiose phosphorylase from Cellvibrio gilvus was examined for its acceptor specificity in the synthetic reaction with glucose-1-phosphate, using substrates in which the C-6 substituent of D-Glc had been altered. A range of disaccharides were also tested for acceptor specificity but only those with (1-->6)-linkages were successful acceptors. Melibiose, gentiobiose, isomaltose and also the monosaccharide glucuronamide were found to react with cellobiose phosphorylase and glucose-1-phosphate giving beta-D-Glcp-(1-->4)-[alpha-D-Galp-(1-->6)]-D-Glcp, beta-D-Glcp-(1-->4)-[beta-D-Glcp-(1-->6)]-D-Glcp, beta-D-Glcp-(1-->4)-[alpha-D-Glcp-(1-->6)]-D-Glcp and beta-D-Glcp-(1-->4)-D-GlcUNp, respectively. These products were purified using a range of chromatographic methods and characterised by NMR and FAB-MS. This is the first time cellobiose phosphorylase has been shown to synthesise trisaccharides.