title: Function of the family-9 and family-22 carbohydrate-binding modules in a modular beta-1,3-1,4-glucanase/xylanase derived from Clostridium stercorarium Xyn10B.
abstract: Clostridium stercorarium Xyn10B having hydrolytic activities on xylan and beta-1,3-1,4-glucan is a modular enzyme composed of two family-22 carbohydrate-binding modules (CBMs), a family-10 catalytic module of the glycoside hydrolases, a family-9 CBM, and two S-layer homologous modules, consecutively from the N-terminus. We investigated the function of family-9 and family-22 CBMs in a modular enzyme by comparing the enzymatic properties of a truncated enzyme composed of two family-22 CBMs and the catalytic module (rCBM22-CM), an enzyme composed of the catalytic module and family-9 CBM (rCM-CBM9), an enzyme composed of two family-22 CBMs, the catalytic module, and family-9 CBM (rCBM22-CM-CBM9), and the catalytic module polypeptide (rCM). Although the addition of family-9 CBM to rCM and rCBM22-CM did not significantly change catalytic activity toward xylan and beta-1,3-1,4-glucan, the addition of family-22 CBM to rCM and rCM-CBM9 drastically enhanced catalytic activity toward xylan and especially beta-1,3-1,4-glucan. Furthermore, the addition of family-22 CBM to rCM and rCM-CBM9 shifted the optimum temperature from 65 degrees C to 75 degrees C, but that of family-9 CBM to rCM and rCBM22-CM did not affect the optimum temperature. These facts suggest that the enzyme properties of Xyn10B were mainly dependent on the presence of the family-22 CBMs but not family-9 CBM.
authors.affiliation: Faculty of Bioresources, Mie University, Tsu, Japan.
authors.forename: Guangshan
authors.initials: G
authors.lastname: Zhao
authors.forename: Ehsan
authors.initials: E
authors.lastname: Ali
authors.forename: Rie
authors.initials: R
authors.lastname: Araki
authors.forename: Makiko
authors.initials: M
authors.lastname: Sakka
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kimura
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sakka
mesh_terms: D001483:Base Sequence; D050260:Carbohydrate Metabolism; D003013:Clostridium / Q000201:enzymology*; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000378:metabolism*; D010957:Plasmids; D013379:Substrate Specificity
chemical_list: D017931:DNA Primers; D006026:Glycoside Hydrolases; D043364:Endo-1,4-beta Xylanases