title: Non-structured amino-acid impact on GH11 differs from GH10 xylanase.
abstract: The Aspergillus niger xylanase (Xyn) was used as a model to investigate impacts of un-structured residues on GH11 family enzyme, because the β-jelly roll structure has five residues (Ser1Ala2Gly3Ile4Asn5) at N-terminus and two residues (Ser183Ser184) at C-terminus that do not form to helix or strand. The N- or/and C-terminal residues were respectively deleted to construct three mutants. The optimal temperatures of XynΔN, XynΔC, and XynΔNC were 46, 50, and 46°C, and the thermostabilities were 15.7, 73.9, 15.5 min at 50°C, respectively, compared to 48°C and 33.9 min for the Xyn. After kinetic analysis, the substrate-binding affinities for birch-wood xylan decreased in the order XynΔC>Xyn>XynΔNC>XynΔN, while the K(cat) values increased in the order XynΔC<XynΔNC<Xyn<XynΔN. The C-terminal deletion increased the GH11 xylanase thermostability and T(opt), while the N- and NC-terminal deletions decreased its thermostability and optimal temperature. The C-terminal residues created more impact on enzyme thermal property, while the N-terminal residues created more impact on its catalytic efficiency and substrate-binding affinity. The impact of non-structured residues on GH11 xylanase was different from that of similar residues on GH10 xylanase, and the difference is attributed to structural difference between GH11 jelly-roll and GH10 (β/α)(8).
authors.affiliation: Life Science College, Henan Agricultural University, Zhengzhou, Henan, China. LLW321@yahoo.com.cn
authors.forename: Liangwei
authors.initials: L
authors.lastname: Liu
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Sun
authors.forename: Pengfei
authors.initials: P
authors.lastname: Yan
authors.forename: Linmin
authors.initials: L
authors.lastname: Wang
authors.forename: Hongge
authors.initials: H
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology*; D020134:Catalytic Domain; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017384:Sequence Deletion; D013379:Substrate Specificity
chemical_list: D043364:Endo-1,4-beta Xylanases