Substrate Specificity of Streptomyces [beta]-Xylanase toward Glucoxylan

To discover the specificity of Streptomyces β-xylanase toward xylan having glucose stubs, glucoxylan was prepared by the hydrogenation of cotton-seed cake glucuronoxylan. The glucoxylan was hydrolyzed by the β-xylanase of Streptomyces olivaceoviridis E-86, and three kinds of glucoxylo-oligosaccharides were isolated from the hydrolysate by chromatographies on a charcoal column, preparative paper partition, and a Toyopearl HW-40F column. The isolated oligosaccharides had the structures of 23-α-glucopyranosylxylotriose, 23-α-(4-O-methyl-glucopyranosyl)xylotriose and 24-α-glucopyranosylxylotetraose. From the structure of the above oligosaccharides and the results of our previous studies, we suggest that the specificity of Streptomyces β-xylanase toward glucose stubs is the same as that toward glucuronic acid stubs, but differs considerably from that toward arabinose stubs.