A novel laccase from the ascomycete Melanocarpus albomyces

A novel laccase from the ascomycete Melanocarpus albomyces was isolated, purified and characterized. The ultraviolet-visible absorption and electron paramagnetic resonance spectra indicated that the three types of coppers were present. Redox potential of the T1 copper of M. albomyces laccase was determined to be 0.46 +/- 0.01 V. The enzyme had very interesting pH and temperature behaviour. It had a pH optimum measured with guaiacol at neutral and slightly alkalic pH and substantial activity still at pH 8. The laccase showed very good thermostability, retaining full activity for two hours at 60degreesC. The gene encoding the M. albomyces laccase was isolated and sequenced. The length of the open reading frame of the M albomyces laccase was 623 amino acid residues. The copper binding residues were well conserved and the amino acid sequence had high homology to other ascomycete laccases. Interestingly the secreted laccase was processed both from the amino and carboxy terminus. The laccase was also crystallized with all four coppers present.