Characterization of manganese-dependent peroxidase isoenzymes from the ligninolytic fungus Phanerochaete flavido-alba.

Phanerochaete flavido-alba is able to decolorize and detoxify olive oil wastewater (OMW) in a process in which simple and polymeric phenols are removed. An unusual acidic MnP is accumulated during the degradation course. This microorganism produces two families of MnPs. MnP1 has an apparent molecular weight of 45 kDa and is secreted as a mixture of isoenzymes with pI ranging from 5.6 to 4.75. MnP2, which is produced as an unique isoenzyme, has an apparent molecular weight of 55.6 Mr and an unusual acidic pI lower than 2.8. The higher specific peroxidase activity for purified MnP2 was for Mn2+ oxidation. Hydroquinone and methylhydroquinone oxidation by MnP2 was Mn2+ dependent, in reaction mixtures without exogenous H2O2. Conversely, ABTS oxidation was Mn2+ independent. Two different DNA fragments (mnpA and mnpB), amplified by PCR, using MnP2 N-terminal sequence and oligonucleotides deduced from two conserved sequences of other MnPs, code for MnPs that belong to the P. chrysosporium mnp2 subfamily on the basis of intron position. The structure of mnpA and mnpB seems to be related to known manganese peroxidase genes, but mnpA encodes an Alanine instead of a Serine (Ser168) regarded as invariant within typical MnPs.