Functional co-expression of human oxidoreductase and cytochrome P450 1A1 in Saccharomyces cerevisiae results in increased EROD activity

A cDNA coding for human oxidoreductase (NADPH-cytochrome P450 reductase) was expressed in S. cerevisiae on a high copy plasmid under control of a constitutive promoter. Microsomes from a transformed strain lacking endogenous oxidoreductase exhibited cytochrome c reductase activity. An apparent Km of 7.3 microM for the substrate NADPH was determined. Expression of human oxidoreductase complemented a mutation in the yeast oxidoreductase gene CPR1 and fully reversed the ketoconazole sensitive phenotype of the respective strain. The 7-ethoxyresorufin-O-deethylase activity of yeast cells expressing human cytochrome P450 1A1 was increased by more than sixteen-fold upon coexpression of human oxidoreductase. These results strongly suggest that a more efficient coupling between the human enzymes might be responsible for the increase in enzyme activity.