Purification of a laccase from fungus combs in the nest of Odontotermes formosanus

A new enzyme was isolated from the fungus combs in the nest of Odontotermes formosanus and identified as a laccase. The single laccase was purified with a purification factor of 16.83 by ammonium sulphate precipitation and anion exchange chromatography, to a specific activity of 211.11 U mg(-1). Its molecular mass was 65 kDa. The optimum pH value and temperature were 4.0 degrees C and 10 degrees C with ABTS as the substrate, respectively. The enzyme activity stabilized at temperatures between 10 degrees C and 30 degrees C and decreased rapidly when the temperature was above 30 degrees C. The V-max and K-m values were 3.62 mu mol min(-1) mg-1 and 119.52 mu M. respectively. Ethanol concentration affected laccase activity, inhibiting 60% of enzyme activity at a concentration of 70%. Metal ions of Mg2+, Ba2+ and Fe2+ showed inhibition on enzyme activity of 17.2%, 5.3% and 9.4%, respectively, with the increase of metal ions concentration from 1 mM to 5 mM. Especially Fe2+ strongly inhibited enzyme activity up to 89% inhibition at a concentration of 1 mM. (C) 2010 Elsevier Ltd. All rights reserved.