Fluorescence Lifetime Analysis of Nitrite Reductase from Alcaligenes xylosoxidansat the Single‐Molecule Level Reveals the Enzyme Mechanism

Lighting the route: Immobilized, fluorescently labeled bacterial nitrite reductase (NiR) has been studied during steady‐state turnover by using single‐molecule fluorescence lifetime imaging spectroscopy. With this method, two populations of single NiR molecules exhibiting different turnover rates can be distinguished. The two populations are tentatively connected by two enzymatic routes: the reduction‐first or the binding‐first pathway (see picture).