Laccase isozymes from Ganoderma lucidum MDU-7: Isolation, characterization, catalytic properties and differential role during oxidative stress

Strain of Ganoderma lucidum MDU-7 produce multiple extracellular isoforms of laccase in submerged culture condition using malt extract as a carbon source and copper sulfate as an inducer. SDS-PAGE followed by MALDI-TOF peptide fingerprinting confirmed laccase isozyme with molecular mass of 24-66 kDa. Two laccase isozymes (Glac H1 and Glac L1)were purified from native-PAGE protein purification method and a comparative catalytic and antioxidant study has been performed. Both of the laccase isozymes have optimum temperature and pH at 50 degrees C and 4.0, respectively. Glac L1 has higher stability in comparison to Glac H1, over wide range of temperature, pH, divalent metal ions and surfactants. The K-m values of Glac L1 and Glac H1 determined for guaiacol, ABTS and O-tolidine were 98 mu M, 26 mu M, 320 mu M and 281 mu M, 29 mu M, 338 mu M, respectively. Glac H1, irrespective to its laccase activity and stability, acts as a better antioxidant than Glac L1. (C) 2015 Elsevier B.V. All rights reserved.