We purified a laccase isoenzyme, Lad 1 from Galerina sp. HC1 using a combination of anion exchange- and hydrophobic interaction chromatography. Lad l has a molecular mass of 64 kDa, an isoelectric point of 4, and 3.35 copper atoms/enzyme molecule. The enzyme has features typical of fungal blue laccases. The sequences of two internal peptides were highly similar to reported laccase sequences from other fungi such as Trametes sp. Lad 1 exhibited optimal activity on substrate 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) at pH 3 and 60 degrees C. It had high stability at <= 20 degrees C and at high pH. Lad 1 exhibited high substrate affinity and the highest catalytic efficiency reported among laccases for ABTS, and among the lowest for syringaldazine. The most potent inhibitors of Lad 1 were sodium azide, sodium cyanide, disulfide reducing agents, and metal ions in the order Li(+) > Sn(2+) > Hg(2+). The laccase efficiently catalyzed demethylation of eucalyptus hard wood Kraft lignin. (C) 2010 Elsevier Ltd. All rights reserved.