Effect of introducing neutral amino acids residues on the thermostability of xylanases XynZF-2
The xylanase XynZF-2 from Aspergillus nigerXZ-3S was analyzed by bioinformatics.Neutral amino acids residues (Cys) were introduced at the N-terminus.The mutated gene xyn-E27C was amplified by site-directed mutagenesis of E27C and expressed in Escherichia coli BL21 (DE3).According to the enzyme properties analysis and compared to the recombinant XynZF-2, results showed that the optimum temperature of mutant Xyn-E27C was 45 ℃, which was increased by 5 ℃.At 40 ℃, compared to XynZF-2 (t1/245℃=55 min), the t1/245℃ of the mutated Xyn-E27C was 100 min, which was increased by 45 min.At 45 ℃, compared to XynZF-2(t1/245℃=7 min), the half-life of the mutated Xyn-E27C was 24 min, which was increased by 17 min.The optimum pH of mutated Xyn-E27C was increased from 5.0 to 5.5, while the pH stability range was from pH 5.0 to 9.0.Therefore, E27C site-directed mutagenesis had important effect on the thermal stability and pH of xylanase XynZF-2.
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