Copper-dependent production of a Pycnoporus coccineus extracellular laccase in Aspergillus oryzae and Saccharomyces cerevisiae

Laccase is a multicopper-containing enzyme that catalyzes the oxidation of phenolic compounds. lcc1 cDNA coding for a secretory laccase of Pycnoporus coccineus was expressed under the maltose inducible amyB promoter in Aspergillus oryzae and under the galactose inducible GAL10 promoter in Saccharomyces cerevisiae. Laccase activities, which were undetectable in the absence of copper, were observed by increasing copper concentrations in the media for both systems. The amounts of secreted laccase protein but not lcc1 mRNA increased in proportion to copper concentrations in A. oryzae. The extracellular activities of native A. oryzae amylase and recombinant RNase-T1 expressed from the same amyB promoter in A. oryzae were constant regardless of copper concentrations. Our results indicate that a high copper concentration is required for the production of active laccase in heterologous hosts and that the copper is required for a posttranscriptional process.