通过N端引入芳香族氨基酸提高木聚糖酶的热稳定性

Improving thermal stability of xylanase by introducing aromatic residues at the N-terminus

摘要:

耐热的木聚糖酶具有用于造纸、麻类脱胶和饲料生产等工业领域的巨大潜力，为了提高11家族碱性木聚糖酶Xyn11A-LC的热稳定性，通过理性设计在N-末端引入了芳香族氨基酸 (T9Y和D14F)。测定野生型和突变体的性质表明，突变体的最适反应温度和热稳定性均获得了提高。突变体的最适反应温度比野生型提高了5 ℃。野生型在65 ℃的Tris/HCl缓冲液 (pH 8.0) 中的半衰期为22 min，而突变体在此条件下的半衰期为106 min。圆二色光谱测定结果显示野生型和突变体的Tm分别为55.3 ℃和67.9 ℃。因此，通过在N-末端引入芳香族氨基酸可以提高11家族木聚糖酶的热稳定性和在高温下的活性。

关键词:木聚糖酶，热稳定性，芳香族氨基酸，疏水作用

Abstract:

Thermophilic and alkalophilic xylanases have great potential in the pulp bleaching industry. In order to improve the thermal stability of an alkaline family 11 xylanase Xyn11A-LC, aromatic residues were introduced into the N-terminus of the enzyme by rational design. The mutant increased the optimum temperature by 5 ℃. The wild type had a half-time of 22 min at 65 ℃ and pH 8.0 (Tris-HCl buffer). Under the same condition, the mutant had the half-time of 106 min. CD spectroscopy revealed that the melting temperature (Tm) values of the wild type and mutant were 55.3 ℃ and 67.9 ℃, respectively. These results showed that the introduction of aromatic residues could enhance the thermal stability of Xyn11A-LC.

Key words:xylanase, thermal stability, aromatic residues, hydrophobic interaction