Novel substrate specificity of a membrane-bound beta-glycosidase from the hyperthermophilic archaeon Pyrococcus horikoshii

A beta-glycosidase gene homolog of Pyrococcus horikoshii (BGPh) was success fully expressed in Escherichia coli. The enzyme was localized in a membrane fraction and solubilized with 2.5% Triton X-100 at 85 degrees C for 15 min , The optimum pH was 6.0 and the optimum temperature was over 100 degrees C , respectively. BGPh stability was dependent on the presence of Triton X-10 0, the enzyme's half-life at 90 degrees C (pH 6.0) was 15 h, BGPh has a nov el substrate specificity with k(cat)/K-m values high enough for hydrolysis of beta-D-Glcp derivatives with long alkyl chain at the reducing end and lo w enough for the hydrolysis of beta-linked glucose dimer more hydrophilic t han aryl- or alkyl-beta-D-Glcp (C) 2000 Federation of European Biochemical Societies.