Molecular cloning and heterologous expression of the gene encoding dihydrogeodin oxidase, a multicopper blue enzyme from Aspergillus terreus.

Aspergillus terreus dihydrogeodin oxidase (DHGO) is an enzyme catalyzing the stereospecific phenol oxidative coupling reaction converting dihydrogeodin to (+)- geodin. We previously reported the purification of DHGO from A. terreus and raised polyclonal antibody against DHGO. From the first cDNA library constructed in lambda gt11 using mRNA from 3-day-old mycelium of A. terreus, four clones were identified using anti-DHGO antibody, but all contained partial cDNA inserts around 280 base pairs. This cDNA fragment was used as a probe to clone the genomic DNA and cDNA for dihydrogeodin oxidase from A. terreus. The sequence of the cloned DHGO genomic DNA and cDNA predicted that the DHGO polypeptide consists of 605 amino acids showing significant homology with multicopper blue proteins such as laccase and ascorbate oxidase. Four potential copper binding domains exist in DHGO polypeptide. The DHGO gene consists of seven exons separated by six short introns. Expression of the DHGO gene in Aspergillus nidulans under the starch or maltose-inducible Taka-amylase A promoter as an active enzyme established the functional identity of the gene. Also, introduction of the genomic DNA for DHGO into Penicillium frequentans led to the production of DHGO polypeptide as judged by Western blot analysis.