Abstract:Site-directed mutagenesises had been done in this work with the consideration of increasing the thermostability of a family 11 xylanase(AoXyn11A) from Aspergillus oryzae.The mutant,AoXyn11AM,was obtained by introducing a disulfide bridge into the N-terminal region of AoXyn11A after N-terminal amino acid homology alignment of AoXyn11A with a thermostable family 11 xylanase,EvXyn11TS.The thermostability of the wild-type enzyme and mutant were analyzed by homology modeling,and assessed by molecular dynamics(MD) simulations.The genes,AoXyn11A and AoXyn11AM,were expressed in Pichia pastoris GS115,respectively.And the effects of temperatures on the thermostability of the expressed AoXyn11A and AoXyn11AMwere analyzed.The results showed the optimal temperature of AoXyn11AMwas raised to 60 ℃ from 55 ℃ of AoXyn11A;after incubated at 50 ℃ and 55 ℃ for 30 min,respectively,the mutant retained 94% and 45% of its original activity while the wild-type enzyme retained 62.5% and 1.4% of its original activity.The mutant not only preserved the major excellent properties of the wild-type enzyme,but also enhanced the thermostability which is potentially useful in industrial applications.
