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

• Ganoderma lucidum MDU-7 produces multiple extracellular isoforms of laccase.
• MALDI–TOF peptide fingerprinting confirmed laccase isozyme with mol mass of 24–66 kDa.
• Two laccase isozymes (Glac H1 and Glac L1) have been successfully purified and characterized.
• Antioxidant property of both the isozymes has been studied.

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 °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 Km values of Glac L1 and Glac H1 determined for guaiacol, ABTS and O-tolidine were 98 μM, 26 μM, 320 μM and 281 μM, 29 μM, 338 μM, respectively. Glac H1, irrespective to its laccase activity and stability, acts as a better antioxidant than Glac L1.

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