The Participation of Cytochromes in the Reduction of Trimethylamine N-oxide by Escherichia coli

Abstract

The participation of cytochrormes of the membrane preparation from Escherichia coli in the reduction of trimethylamine N-oxide (TMO) was investigated spectrophotometrically.
Two physiological reductants, formate and NADH, could reduce the cytochromes in the membrane preparation. The difference spectra of the cytochromes reduced by both the reductants were entirely the same as the spectrum recorded with Na₂S₂O₄ as a reductant; all these spectra had 3 major peaks: at 555 nm, 526 nm, and 425-426 nm. The low-temperature spectrum obtained at liquid nitrogen temperature (77K) revealed that the cytochromes are composed of multiple components. The formate- and NADH-reduced cytochromes were gradually reoxidized by TMO, suggesting the participation of the cytochromes in TMO reduction. 2-Heptyl-4-hydroxyquinoline N-oxide (HOQNO) partially inhibited the reoxidation by TMO. In connection with this HOQNO-inhibition, different types of cytochrome components are discussed.