Activity of oxidative enzymes in fungal mycelia from grassland and forest soils

In the vegetation periods of 1994 and 1995, fungus‐colonized soil samples from around the base of fruit bodies of basidiomycete fungi were excised. They were collected from fairy rings on grass‐ and woodlands and from stands of ectomycorrhizal fungi. Control samples devoid of conspicuous mycelia originated from adjacent plots with a comparable vegetation and soil structure. Water extraction and spectrophotometric analysis of fungus‐colonized samples indicated the presence of several cellfree polyphenol oxidases, peroxidases, manganese peroxidases, hydroxylases, aromatic‐ring cleavage dioxygenases, and esterases as well as active oxygen species. Tests for ligninolytic activity were in part positive. The activities of enzymes involved in the catalysis of H 2 O 2 , the essential co‐substrate of ligninolytic peroxidases, were also detected. Unvegetated control soils contained occasional traces of free polyphenol oxidases and peroxidases. Vegetated control samples were dominated by the activity of guaiacol peroxidase, which is known to be linked with plant tissue. It is concluded that basidiomycetous mycelia grown in the field are associated with the activities of enzymes which directly catalyze the degradation of lignin, some humic material in soil, and aromatic xenobiotics by hydroxylation, oxidation, and cleavage of aromatic ring structures. Further enzymes detected by their activities may be indirectly involved in these degradation processes by forming highly reactive substrate radicals, active oxygen species, and higher‐valency metal ions with considerable oxidative capacity.