Two H2O2‐dependent oxidases found in the extracellular medium of the white rot fungus Phanerochaete chrysosporium were separated by chromatography on blue agarose. The first enzyme fraction to elute from the column generated ethylene from 2‐keto‐4‐thiomethylbutyric acid (KTBA) in the presence of veratryl alcohol, and catalyzed the α,β cleavage of the diarylpropane 1‐(3,4‐diethoxyphenyl)1,3‐dihdyroxy‐(4‐methoxyphenyl)propane (I). During the diarylpropane cleavage, 18O from 18O2 was incorporated specifically into the α‐position of the product 1‐(4‐methoxyphenyl)1,2‐dihdyroxyethane (III), suggesting that this enzyme is an H2O2‐dependent oxygenase. The second enzyme which binds to blue agarose is an Mn2+‐dependent, lactate‐activated peroxidase. The enzyme catalyzed the oxidation of phenol red, o‐dianisidine, Poly R, and a variety of other dyes. It was also capable of decarboxylating vanillic acid.

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A novel selection marker gene for transformation of the white-rot basidiomycete Pleurotus ostreatus was developed by introducing a point mutation in a gene which encodes the iron-sulfur protein (Ip) subunit of succinate dehydrogenase. The mutant gene, CbxR, encodes a modified Ip subunit with an amino-acid substitution (His239 to Leu) and confers resistance to the systemic fungicide, carboxin. The DNA sequence was integrated ectopically in the chromosome of the transformants. This is the first report of a homologous marker gene which is available for the molecular breeding of an edible mushroom.