CHARACTERIZATION OF A LACCASE SECRETED BY ARMILLARIA-MELLEA PATHOGENIC FOR GENISTA

A laccase has been purified with high yields and characterised from th e in vitro culture medium of Armillaria mellea. The enzyme has an appa rent molecular mass of 80 kDa, and it appears as a single band on PAGE electrophoresis. Under denaturing conditions, the enzyme gives two ne w bands on PAGE, with molecular masses of about 30 and 40 kDa respecti vely. The UV-visible spectrum demonstrates the presence of type I and type III copper. The total content of copper is four atoms per molecul e of enzyme, and the carbohydrate content is high (37-40%). The isoele ctric point is low, around 3.1. The enzyme oxidises a range of differe nt phenolic substrates typical for fungal laccases. Moreover, the abil ity of this laccase to oxidise the reduced form of iron may account fo r a competition for this metal with the plant tissues during growth of the fungus within the host.