Fusion of family 2b carbohydrate-binding module increases the catalytic activity of a xylanase from Thermotoga maritima to soluble xylan

A family 2b carbohydrate-binding module from Streptomyces thermoviolaceus STX-II was fused at the carboxyl-terminus of XynB, a thermostable and single domain family 10 xylanase from Thermotoga maritima, to create a chimeric xylanase. The chimeric enzyme (XynB-CBM2b) was purified and characterized. It displayed a pH-activity profile similar to that of XynB and was stable up to 90degreesC. XynB-CBM2b bound to insoluble birchwood and oatspelt xylan. Whereas its hydrolytic activities toward insoluble xylan and p-nitrophenyl-p-xylopyranoside were similar to those of XynB, its activity toward soluble xylan was moderately higher than that of XynB. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.