Molecular characterization of a novel peroxidase isolated from the ligninolytic fungus Pleurotus eryngii.
A haem peroxidase different from other microbial, plant and animal peroxidases is described. The enzyme is secreted as two isoforms by dikaryotic Pleurotus eryngii in peptone-containing liquid medium. The corresponding gene, which presents 15 introns and encodes a 361-amino-acid protein with a 30-amino-acid signal peptide, was isolated as two alleles corresponding to the two isoforms. The alleles differ in three amino acid residues and in a seven nucleotide deletion affecting a single metal response element in the promoter. When compared with Phanerochaete chrysosporium peroxidases, the new enzyme appears closer to lignin peroxidase (LiP) than to Mn-dependent peroxidase (MnP) isoenzymes (58-60% and 55% identity respectively). The molecular model built using crystal structures of three fungal peroxidases as templates, also showed high structural affinity with LiP (C alpha-distance 1.2 A). However, this peroxidase includes a Mn2+ binding site formed by three acidic residues (E36, E40 and D175) near the haem internal propionate, which accounts for the ability to oxidize Mn2+. Its capability to oxidize aromatic substrates could involve interactions with aromatic residues at the edge of the haem channel. Another possibility is long-range electron transfer, e.g. from W164, which occupies the same position of LiP W171 recently reported as involved in the catalytic cycle of LiP.
Ruiz-Dueñas
F J
FJ
Department of Molecular Microbiology, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain.
Martínez
M J
MJ
Martínez
A T
AT
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004271:DNA, Fungal; D005656:Fungal Proteins; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008345:Manganese; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009195:Peroxidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010544:Peroxidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020076:Pleurotus / Q000201:enzymology* / Q000235:genetics; D011487:Protein Conformation; D017421:Sequence Analysis