Menadione-dependent reduction of tertiary amine N-oxide by rat liver cytosol.

This study demonstrates the menadione-dependent reduction of imipramine N-oxide, a tertiary amine N-oxide, to imipramine by rat liver cytosol in the presence of NADH or NADPH. A mechanism for the cytosolic reduction of the tertiary amine N-oxide is proposed. Menadione is converted to its reduced form by a menadione-reducing enzyme such as DT-diaphorase and the reduced pyridine nucleotide, followed by reduction of the tertiary amine N-oxide to the amine by the heme group of catalytic hemoproteins in the presence of reduced menadione as an electron donor.