Purification, biochemical characterization and dye decolorization capacity of an alkali-resistant and metal-tolerant laccase from Trametes pubescens

Extracellular laccase (Tplac) from Trametes pubescens was purified to homogeneity by a three-step method, which resulted in a high specific activity of 18.543 U mg(-1), 16.016-fold greater than that crude enzyme at the same level. Tplac is a monomeric protein that has a molecular mass of 68 kDa. The enzyme demonstrated high activity toward 1.0 mM ABTS at an optimum pH of 5.0 and temperature of 50 degrees C, and under these conditions, the catalytic efficiency (k(cat)/K-m) is 8.34 s(-1) mu M-1. Tplac is highly stable and resistant under alkaline conditions, with pH values ranging from 7.0 to 10.0. Interestingly, 88% of initial enzyme activity was maintained in the presence of metal ions at 25.0 mM, leading to an increase in substrate affinity, which indicated that the laccase is highly metal-tolerant. These unusual properties demonstrated that the new fungal laccase Tplac has potentials for the specific industrial environmental applications.(C) 2012 Elsevier Ltd. All rights reserved.