Pyranose 2-oxidase from Phanerochaete chrysosporium--expression in E. coli and biochemical characterization

The presented work reports the isolation and heterologous expression of the p2ox gene encoding the flavoprotein pyranose 2-oxidase (P2Ox) from the basidiomycete Phanerochaete chrysosporium. The p2ox cDNA was inserted into the bacterial expression vector pET21a(+) and successfully expressed in Escherichia coli. We obtained active, fully flavinylated recombinant P2Ox in yields of approximately 270 mg/l medium. The recombinant enzyme was provided with an N-terminal T7-tag and a C-terminal His(6)-tag to facilitate simple one-step purification. We obtained an apparently homogenous enzyme preparation with a specific activity of 16.5 U/mg. Recombinant P2Ox from P. chrysosporium was characterized in some detail with respect to its physical and catalytic properties, both for electron donor (sugar substrates) and - for the first time - alternative electron acceptors (1,4-benzoquinone, substituted quinones, 2,6-dichloroindophenol and ferricenium ion). As judged from the catalytic efficiencies k(cat)/K(m), some of these alternative electron acceptors are better substrates than oxygen, which might have implications for the proposed in vivo function of pyranose 2-oxidase.