Amino Acid Mutations within the CYP2D6 Active Site Affect Product Distribution While Effects of NADPH Coupling are Varied
Oswalt, Alexandria K.
MetadataShow full item record
Human cytochrome P450s have a vital role in metabolism of all classes of pharmaceutical drugs. Human CYP2D6 is responsible for about 20%of drug metabolism, and has the most polymorphisms in the class of P450s. These polymorphisms result in varying metabolic activity as well as product distribution. One possible explanation for varying activity is that certain allelic variants uncouple the P450 reaction with NADPH, which was the source of electrons needed to activate the heme in the active site. The purpose of this study was two-fold: to determine the product distribution of several 2D6 variants with regard to metabolism of three substrates, dextromethorphan, bufuralol, and SCH 66712, and to determine the percent coupling of NADPH consumption of each of the variants during bufuralol metabolism. Five naturally occurring variants as well as one artificially mutated variant were previously studied and found to have widely varying activity. The same variants were used in the present metabolite and NADPH coupling study. Analysis of metabolite profiles revealed a novel dehydrogenation product of bufuralol metabolism as well as a novel mono-oxygenation product of dextromethorphan metabolism. Reduced or lost metabolites with reaction initiation by the oxygen surrogate CuOOH suggests that using an oxygen surrogate shifts the distribution of oxygenating species and causes a shift in preferred oxidation reactions byCYP2D6. Reduced coupling in variants *34, *17-2, and *17-3 suggest that Arg296, a residue that is mutated in these variants, may be involved in electron transfer from NADPH-P450 reductase to the active site of CYP2D6.