Ligninolytic enzymes of the fungus Irpex lacteus (Polyporus tulipiferae): isolation and characterization of lignin peroxidase

The extracellular ligninolytic enzymatic activity of the fungus Irpex lacteus (Polyporus tulipiferae) grown in nonimmersed liquid culture under nitrogen limitation was characterized. Laccase (LAC), manganese-dependent lignin peroxidase (MNP) and lignin peroxidase (LIP) activities were detected and their formation followed a temporal sequence peaking at day 4, 7 and 11, respectively. Three LIP isozymes, designated LIP1, LIP2 and LIP3, were isolated from manganese-depleted cultures, and exhibited molecular masses of 41, 41 and 44 kDa, respectively, pIs of 5.0, 4.9 and <4.6, respectively, and to 4–5% glycosylation. All isozymes were active towards a range of phenolic substrates, with veratryl alcohol being the preferred one. The kinetics constants obtained for veratryl alcohol and H2O2 were comparable to those of LIPs from other white-rot fungi. The N-terminal sequences of LIP1 and LIP2 were identical and presented 64% similarity with LIP3, and were closely related to the amino acid sequences of LIP isozymes from Phlebia radiata (LIG III), Trametes versicolor (LIG C) and Phanerochaete chrysosporium (GLG2, GLG3 and GLG4). Sequence alignment with other reported LIPs revealed fewer identical or similar residues. Taken together, these data suggest that despite similarity in catalytic properties, kinetics parameters and spectral characteristics, there seems to be high degree of diversity among LIPs of different white-rot fungi.