Enhanced thermostability of a mesophilic xylanase by N-terminal replacement designed by molecular dynamics simulation.

Background Xylanases have attracted much attention owing to their potential applications. The applicability of xylanases, however, was bottlenecked by their low stabilities at high temperature or extreme pH. The purpose of this work was to enhance the thermostability of a mesophilic xylanase by N-terminal replacement. Results The thermostability of AoXyn11, a mesophilic family 11 xylanase from Aspergillus oryzae, was enhanced by replacing its N-terminal segment with the corresponding one of EvXyn11TS, a hyperthermotolerant family 11 xylanase. A hybrid xylanase with high thermostability, NhXyn1157, was predicted by molecular dynamics (MD) simulation. An NhXyn1157-encoding gene, Nhxyn1157, was then constructed as designed theoretically, and overexpressed in Pichia pastoris. The temperature optimum of recombinant NhXyn1157 (re-NhXyn1157) was 75 °C, much higher than that of re-AoXyn11. Both xylanases were thermostable at 65 and 40 °C, respectively. Additionally, the pH optimum and stability of re-NhXyn1157 were 5.5 and at a range of 4.0–8.5. Its activity was not significantly affected by metal ions tested and EDTA, but strongly inhibited by Mn2+ and Ag+. Conclusion This work obviously enhanced the thermostability of a mesophilic xylanase, making re-NhXyn1157 a promising candidate for industrial processes. It also provided an effective technical strategy for improving thermostabilities of other mesophilic enzymes. © 2013 Society of Chemical Industry