Non-Structured Amino-Acid Impact on GH11 Differs from GH10 Xylanase

作者：Liu, Liangwei^*; Sun, Xiaofeng; Yan, Pengfei; Wang, Linmin; Chen, Hongge

来源：PLos One, 2012, 7(9): e45762.

DOI：10.1371/journal.pone.0045762

• TRICHODERMA-REESEI ENDO-1,4-BETA-XYLANASE-II
• DISULFIDE BRIDGE
• ENZYMATIC-ACTIVITY
• THERMAL-STABILITY
• SUBSTRATE-BINDING
• THERMOSTABILITY
• COMBINATION
• DELETION
• DOMAINS
• REGION

The Aspergillus niger xylanase (Xyn) was used as a model to investigate impacts of un-structured residues on GH11 family enzyme, because the beta-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 Xyn Delta N, Xyn Delta C, and Xyn Delta NC were 46, 50, and 46 degrees C, and the thermostabilities were 15.7, 73.9, 15.5 min at 50 degrees C, respectively, compared to 48 degrees C and 33.9 min for the Xyn. After kinetic analysis, the substrate-binding affinities for birch-wood xylan decreased in the order Xyn Delta C>Xyn>Xyn Delta NC>Xyn Delta N, while the K-cat values increased in the order Xyn Delta C<Xyn Delta NC<Xyn<Xyn Delta N. 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 (beta/alpha)(8).

• 出版日期2012-9-21
• 单位河南农业大学