Purification, characterization and sequence analysis of a laccase from the ascomycete Mauginiella sp.

A laccase from the ascomycete Mauginiella sp. was purified to electrophoretic homogeneity and biochemically characterized. The molecular mass of the laccase was 63 kDa as determined by mass spectrometry and it existed as six isoforms with isoelectric points in the range of 4.8–6.4. The laccase showed activity towards the typical substrates: 2,2′-azinobis-(3-ethylbenzothiazoline)-6-sulphonate (ABTS), guaiacol, dimethoxyphenol (2,6-DMP), and syringaldazine. The pH optima on guaiacol, 2,6-DMP and ABTS were 4, 3.5 and 2.4, respectively. The enzyme was strongly, 98%, inhibited by 1 mM NaN3 and 88% by 1 mM KCN. The laccase was stable at neutral pH, retaining 80% activity after 24 h at pH 6–8. The enzyme was sensitive to high temperatures: the half-life at 70 °C was only 3 min. A fragment of the laccase gene was isolated and its nucleotide sequence was determined. The laccase gene showed high identity to the laccase genes lcc1 and lcc2 of the basidiomycetes Trametes versicolor and Trametes villosa, respectively.