Structural and Biochemical Characterization of CYP2D6-Mediated Dextromethorphan Metabolism Using Isonitrile-based Analogs

Abstract ID 97229 Poster Board 234 Cytochrome P450 2D6 (CYP2D6) plays an important role in drug metabolism, being responsible for the metabolism of ∼20% of pharmaceutical compounds. Dextromethorphan metabolism has long been used as a marker of CYP2D6 activity, with the enzyme performing an O-demethylation to yield the more hydrophilic major product dextrorphan. CYP2D6 is also capable of performing an N-demethylation to yield the minor product 3-methoxymorphinan, which is the primary product produced by CYP3A4. However, we do not fully understand the structural mechanisms involved in determining the orientation of dextromethorphan in the CYP2D6 active site. To our knowledge, there have been no successful attempts to solve the structure of CYP2D6 with dextromethorphan or its products. To better understand the metabolic process, we designed a series of inhibitors based on the N- and O-demethylation products of dextromethorphan. We substituted the N- or O-methyl group with an isonitrile group, a group found to coordinate tightly to the heme iron, resulting in a stable complex. Described here is the structural and functional characterization of CYP2D6 with these isonitrile-based inhibitors, including spectral characteristics, binding assays, inhibition assays, and preliminary structural data. NIH