Molecular cloning of aryl-alcohol oxidase from the fungus Pleurotus eryngii, an enzyme involved in lignin degradation

Aryl-alcohol oxidase (AAO), an extracellular enzyme characteristic of fungi from the genus Pleurotus , constitutes a source for H 2 O 2 required in lignin biodegradation. The gene aao has been cloned, sequenced and characterized for the first time in Pleurotus eryngii . Both cDNA and genomic libraries were screened with probes obtained by PCR using as primers oligonucleotides corresponding to the N-terminus and internal sequences of AAO. DNA sequences from positive clones showed a unique open reading frame of 1779 nucleotides interrupted by 12 introns. The conceptual translation of the protein agrees with the partial amino acid sequences obtained from protein sequencing. A search for proteins with related amino-acid sequences revealed that glucose oxidase from Aspergillus niger has 33% identity and 51% similarity. A comparison with other oxidoreductases showed common motifs in both N- and C-terminal regions corresponding, respectively, to the FAD-binding region and the enzyme active site. However, AAO probably has structural differences with other oxidases, as deduced from its unique ability to generate H 2 O 2 from the oxidation of aromatic alcohols.