PURIFICATION AND CHARACTERIZATION OF 2 LIGNIN PEROXIDASE ISOZYMES PRODUCED BY BJERKANDERA SP. STRAIN BOS55

The white-rot fungus Bjerkandera sp. strain BOS55 excretes at least se ven lignin peroxidase (LIP) isozymes. Two of these, LiP-2 and LiP-5 (m olecular weight 40-42 kDa), were purified to homogeneity, Both isozyme s had the same N-terminal amino acid sequence which showed strong homo logy with LiP isozymes produced by other white-rot fungi, The kinetics of both isozymes were similar, LiP-5 oxidized veratryl alcohol optima lly only in the presence of H2O2 near pH 3.0 (16.7 U/mg) and LiP-2 did this below pH 2.5 (33.8 U/mg), Also at normal physiological pHs for f ungal growth (pH 5.0-6.5) both isozymes were still active, Further cha racterization of LiP-2 and LiP-5 revealed that the K-m for H2O2 strong ly decreased with increasing pH, As a result of this the catalytic eff iciency (TN/K-m) calculated on the basis of the K-m for H2O2 in the ox idation of veratryl alcohol was constant over wide pH range. (C) 1998 Federation of European Biochemical Societies.