MANGANESE PEROXIDASES OF THE WHITE-ROT FUNGUS PHANEROCHAETE SORDIDA

The ligninolytic enzymes produced by the white rot fungus Phanerochaet e sordida in liquid culture were studied. Only manganese peroxidase (M nP) activity could be detected in the supernatant liquid of the cultur es. Lignin peroxidase (LiP) and laccase activities were not detected u nder a variety of different culture conditions. The highest MnP activi ty levels were obtained in nitrogen-limited cultures grown under an ox ygen atmosphere. The enzyme was induced by Mn(II). The initial pH of t he culture medium did not significantly affect the MnP production. Thr ee MnP isozymes were identified (MnPI, MnPII, and MnPIII) and purified to homogeneity by anion-exchange chromatography followed by hydrophob ic chromatography. The isozymes are glycoproteins with approximately t he same molecular mass (around 45 kDa) but have different pIs. The pIs are 5.3, 4.2, and 3.3 for MnPI, MnPII, and MnPIII, respectively. The three isozymes are active in the same range of pHs (pHs 3.0 to 6.0) an d have optimal pHs between 4.5 and 5.0. Their amino-terminal sequences , although highly similar, were distinct, suggesting that each is the product of a separate gene.