Isolation and cDNA cloning of novel hydrogen peroxide-dependent phenol oxidase from the basidiomycete Termitomyces albuminosus

A novel hydrogen peroxide-dependent phenol oxidase (TAP) was isolated from the basidiomycete Termitomyces albuminosus. TAP is an extracellular monomeric enzyme with an estimated molecular weight of 67 kDa. The purified enzyme can oxidize various phenolic compounds in the presence of hydrogen peroxide, but cannot oxidize 3,4-dimethoxybenzyl (veratryl) alcohol. Mn-II was not required for catalysis by TAP. The optimum pH for TAP activity was 2.3, which is the lowest known optimum pH for a fungal phenol oxidase. The cDNA encoding TAP was cloned with reverse transcription-polymerase chain reaction (RT-PCR) using degenerate primers based on the N-terminal amino acid sequence of TAP and 5' rapid amplification of cDNA ends (RACE)PCR. The cDNA encodes a mature protein of 449 amino acids with a 55-amino-acid signal peptide. The deduced amino acid sequence of TAP showed 56% identity with dye-decolorizing heme peroxidase (DYP) from the ascomycete Geotrichum candidum Dec 1, but no homology with other known peroxidases from fungi.