葡聚糖修饰漆酶的制备及其催化特性和稳定性

将经NaIO₄氧化处理的葡聚糖（500×10³）连接在漆酶分子上以提高漆酶在酸性溶液环境中的稳定性。HPLC和SDS-PAGE分析表明葡聚糖修饰漆酶的分子量在200×10³以上。荧光光谱和圆二色性光谱分析表明修饰漆酶保持了天然漆酶的三级和二级结构。酶催化反应显示修饰漆酶与天然漆酶具有类似的底物亲和性和催化活性，而其在酸性条件下的稳定性显著提高。通过葡聚糖修饰使得漆酶在pH 3,50℃下的酶活半衰期从0. 07 h提高到17. 1 h，在含30%（体积）乙腈, pH 3下的酶活半衰期从0. 11 h提高到10. 3 h。在不同pH下测定修饰漆酶在216 nm处的圆二色性光谱，结果显示偶联葡聚糖增强了漆酶分子的结构稳定性，提高了其在高温及有机溶剂存在下的催化活性。

Dextran conjugated laccase and its catalytic property and stability

NaIO₄ oxidized dextran (500×10³) conjugated laccase was prepared to enhance the laccase catalytic stability in acidic pH condition. The dextran conjugated laccase had a molecular weight over 200×10³, as determined by HPLC and SDS-PAGE. Fluorescence and circular dichroism (CD) spectra showed that the conjugated laccase maintained the tertiary and secondary structures of the native laccase. While the conjugated laccase showed similar substrate specificity, catalytic activity, as compared to its native counterpart, the enzyme stability at acidic pH values was significantly improved. The half-life of enzymatic activity was extended from 0. 07 h to 17. 1 h at 50℃. In the presence of 30% (vol) acetonitrile, the half-life of enzyme activity was also extended from 0. 11 h to 10. 3 h. CD spectrum at 216 nm and at different pH values indicated that the conjugation with dextran strengthened the molecular structure of laccase and, consequently, enhanced its catalytic capability at a high temperature and in the presence of organic solvent.