AGROBACTERIUM-TUMEFACIENS BETA-GLUCOSIDASE IS ALSO AN EFFECTIVE BETA-XYLOSIDASE, AND HAS A HIGH TRANSGLYCOSYLATION ACTIVITY IN THE PRESENCEOF ALCOHOLS

Agrobacterium tumefaciens beta-glucosidase, Cbg1 was extensively chara cterised and found to be a retaining aryl-glucosidase and an aryl-xylo sidase. Cbg1s specificity for p-nitrophenyl beta-D-xylopyranoside was 73% that for p-nitrophenyl beta-D-glucopyranoside when measured by the ratio k(cat)/K-m. The enzyme also hydrolysed p-nitrophenyl beta-D-fuc opyranoside, and p-nitrophenyl beta-D-galactopyranoside with moderate efficiency. The enzyme released only terminal glucose from p-nitrophen yl beta-cellobioside and had a 20000-fold preference for its natural s ubstrate coniferin over cellobiose as indicated by the ratio k(cat)/K- m. The enzyme was activated in the presence of 20 mM l-propanol, l-but anol, l-pentanol, 1-hexanol, 1-heptanol, and l-octanol. In the case of butanol this activation was investigated and shown to be due to trans glycosylation activity with over 80% of p-nitrophenyl beta-D-glucopyra noside being converted to l-butyl beta-D-glucopyranoside in the presen ce of Cbg1 and 100 mM I-butanol. (C) 1998 Elsevier Science B.V. All ri ghts reserved.