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 H2O2 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 we re screened with probes obtained by PCR using as primers oligonucleotides c orresponding to the N-terminus and internal sequences of AAO. DNA sequences from positive clones showed a unique open reading frame of 1779 nucleotide s interrupted by 12 introns. The conceptual translation of the: protein agr ees with the partial amino acid sequences obtained from protein sequencing. A search for proteins with related amino-acid sequences revealed that gluc ose oxidase from Aspergillus niger has 33 degrees, identity and 51% similar ity. A comparison with other oxidoreductases showed common motifs in both N - and C-terminal regions corresponding. respectively, to the FAD-binding re gion and the enzyme active site. However, AAO probably has structural diffe rences with other oxidases, as deduced from its unique ability to generate H2O2 from the oxidation of aromatic alcohols.