Abstract:

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.