Chiang Mai Journal of Science

The extracellular laccase produced by Mycena purpureofusca was purified and characterized biochemically and biologically. The molecular mass of the laccase was determined from the analysis of SDS-PAGE following purification with anion exchange chromatography. The purified laccase showed a relative molecular mass of 61.7 kDa. Laccase activity was detected in culture filtrate of M. purpureofusca with ABTS as substrate, optimum pH being 2.2 and optimum temperature at 50°C. The enzymatic activity was stable at neutral pH and temperatures between 10 and 30°C. The laccase activity decreased rapidly when the temperature was above 30°C for 1h. The values of kinetic parameters Km and Vmax for purified laccase were 0.296 (mM) and 0.0645 (mM/min), respectively. Among the metal ions used, Fe³⁺, Mn²⁺ , Cu²⁺, Ag⁺, Ca²⁺, Ba²⁺ and Zn²⁺ were found to have a slightly stimulating effect on the enzyme activity at the concentrations of 0.05 mM. The enzyme activity can be enhanced by 18.7% and 130.5% when Ag⁺ was added to the medium at the concentration of 0.05 and 0.5 respectively. On the contrary, Fe²⁺ strongly inhibited enzyme activity up to 98% at a concentration of 0.05 and 0.5 mM.