(Invited) Molecular Mechanism of NO Reduction By Bacterial Nitric Oxide Reductases

Abstract

Bacterial nitric oxide reductase (NOR) catalyzes the NO reduction reaction (2NO + 2H+ + 2e- --> N2O + H2O) at its active site, which is a binuclear center comprised by heme (heme b 3) and non-heme iron (FeB). In the enzymatic reaction by NOR, three short-lived intermediates have been proposed for the coordination of two molecules of NO to the binuclear center; i.e., trans-, cis-heme b 3- and cis-FeB-coordinations. To establish the molecular mechanism of the NO reduction by NOR, we have been studying the time-resolved spectroscopies to characterize the coordination and electronic structures of the intermediates, which are appeared in the micro- to milli-second time region after the reaction of the ferrous enzyme with the NO molecule(s). On the basis of the time-resolved optical, ESR and IR spectral changes, we have proposed that the trans-mechanism seem favorable for the NO reduction mechanism by bacterial NOR. We will discuss the NOR reaction with referring their crystallographic structural data which we reported.