Cytochrome b5 reductase-cytochrome b5 as an active P450 redox enzyme system in Phanerochaete chrysosporium: Atypical properties and in vivo evidence of electron transfer capability to CYP63A2

► First report on kinetic characterization of cytochrome b5 reductase from fungi. ► Cyt b5r showed no reduction of ferricyanide and a direct reduction of cyt c. ► Cyt b5r followed ping-pong type enzyme kinetic mechanism for reduction of cyt b5. ► First coexpression of CYP63A2 and its homologous redox systems and catalytic analysis. ► First report in a fungus showing that Cyt b5r-b5 can transfer electrons to P450.