Biochemical and molecular characterization of a novel lacease from selective lignin-degrading white-rot fungus Echinodontium taxodii 2538

A novel lacease was isolated and characterized from a new selective lignin-degrading white-rot fungus Echinodontium taxodii 2538, in which a high yield of lacease was obtained. No lacease isoenzyme was detected in the synthetic liquid media. The purified lacease (designated as EtL2538) had an apparent molecular mass of 56kDa, pl value of 3.1, and N-terminal amino acid sequence of GIGPVTDLHIVNAAV. EtL2538 showed optimum pH at 3.0 and optimum temperature at 60[degrees]C using ABTS as the substrate. EtL2538 revealed superior thermostability, and retained over 80% of its original activity after incubation for 2 h at 50 [degrees]C. The lacease gene, etl2538, was also cloned and sequenced. This gene encoded a mature lacease protein containing 499 amino acids (aa) preceded by a signal peptide of 21 aa, and the deduced protein sequence contained four copper-binding conserved domains of typical lacease protein. EtL2538 was further used in lignin oxidation and dye decolorization. Even without the existence of redox mediators, EtL2538 could cleave the methoxyl groups and beta -O-4 ether linkages in lignin from bamboo, and significantly decolorize malachite green and RBBR. These novel properties of EtL2538 may render it as a potential biocatalyst for biotechnological and environmental applications.