Molecular and enzymatic characterisation of extra- and intracellular laccases from the acidophilic ascomycete Hortaea acidophila.

The pigmented ascomycete Hortaea acidophila is able to grow at a pH as low as 0.6 and produces laccases that are involved in melanin synthesis. We now present data on an extracellular and an intracellular laccase which exhibit a high stability at low pH. Furthermore, the optimum for enzyme acitivity is extraordinarily low with pH 1.5 for the intracellular laccase with 2,6-dimethoxyphenol (DMOP) as substrate. Two complete laccase gene sequences of H. acidophila were amplified by inverse polymerase chain reaction (PCR). Whereas the deduced protein laccase I contains an predicted N-terminal signal sequence for protein export, laccase II does not and thus may represent the intracellular laccase. The acidophilic character of both laccases seems to be reflected in their primary structure.