Extracellular peroxidase activity at the hyphal tips of the white-rot fungus Phanerochaete crassa WD1694

The white-rot fungus Phanerochaete crassa WD1694 was cultivated and peroxidase activity staining was performed to determine the sites at which the extracellular peroxidase reaction actually occurs in vivo. Although the ligninolytic peroxidases were found in the culture filtrates, the culture medium did not show a color reaction. However, a particularly strong color reaction was observed on the hyphal tips. Visible spectra and absorbance of the staining were analyzed by microspectrophotometry, and the catalytic rates of the peroxidase reaction at the hyphal tips were calculated. The estimated catalytic rate of the peroxidase reaction at the hyphal tips peaked at 794 μM/min, expressed as the consumption rate of H₂O₂, on day 3 of the cultivation. Analysis of the extracellular enzyme eluted with 0.1% Tween 80 from the mycelium revealed that manganese peroxidase accounted for 89% of all the peroxidase activity measured. The results clearly showed the existence of the concentrated manganese peroxidase reaction around the hyphal tips of the organism.