title: Essential role of the family-22 carbohydrate-binding modules for beta-1,3-1,4-glucanase activity of Clostridium stercorarium Xyn10B.
abstract: Clostridium stercorarium Xyn10B is a modular enzyme comprising two family-22 carbohydrate-binding modules (CBMs), a family-10 catalytic module of glycoside hydrolases, a family-9 CBM, and two S-layer homologous modules consecutively from the N-terminus. To investigate the role of the family-22 CBMs, truncated proteins were constructed: a recombinant catalytic module polypeptide (rCD), a CBM polypeptide composed of two family-22 CBMs (rCBM) and a polypeptide composed of the family-22 CBMs and the catalytic module (rCBM-CD). We found that rCBM-CD was highly active toward beta-1,3-1,4-glucan; however, rCD was negligibly active toward the same substrate. The V(max)/K(m) value of rCBM-CD for beta-1,3-1,4-glucan was 7.8 times larger than that for oat-spelt xylan, indicating that rCBM-CD should be specified as a beta-1,3-1,4-glucanase rather than a xylanase despite the fact that family-10 catalytic modules are well-known xylanase modules. These results indicate that the family-22 CBMs in rCBM-CD are essential for hydrolysis of beta-1,3-1,4-glucan.
authors.affiliation: Faculty of Bioresources, Mie University, 1515 Kamihamacho, Tsu 514-8507, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Araki
authors.forename: Mursheda K
authors.initials: MK
authors.lastname: Ali
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
authors.forename: Kunio
authors.initials: K
authors.lastname: Ohmiya
mesh_terms: D003013:Clostridium / Q000201:enzymology*; D004795:Enzyme Stability; D005936:Glucans / Q000378:metabolism; D006868:Hydrolysis; D046911:Macromolecular Substances; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding; D021122:Protein Subunits; D013379:Substrate Specificity; D013696:Temperature; D014995:Xylosidases / Q000378:metabolism*; D047071:beta-Glucans
chemical_list: D005936:Glucans; D046911:Macromolecular Substances; D011134:Polysaccharides; D021122:Protein Subunits; D047071:beta-Glucans; C067858:beta-glucan, (1-3)(1-4)-; D014995:Xylosidases