Stimulatory effect of FMN and methyl viologen on cytochrome P-450 dependent reduction of tertiary amine N-oxide

Abstract FMN or methyl viologen stimulated anaerobic reduction of tertiary amine N-oxides by liver microsomes and this stimulatory effect was completely inhibited by carbon monoxide. Spectral study indicated that FMN or methyl viologen is reduced by NADPH-cytochrome c reductase and reduced FMN or methyl viologen is reoxidized by cytochrome P-450 in the presence of tertiary amine N-oxides. In the presence of FMN, xanthine oxidase-hypoxanthine system rapidly reduced tiaramide N-oxides through the reduction of cytochrome P-450: the maximum reduction rate of tiaramide N-oxide was about 100 nmoles/mg protein/min.