Trapping of a Putative Intermediate in the Cytochrome Nitrite Reductase (ccNiR)-Catalyzed Reduction of Nitrite: Implications for the ccNiR Reaction Mechanism.

Cytochrome nitrite reductase (ccNiR) is a periplasmic, decaheme homodimeric enzyme that catalyzes the six-electron reduction of nitrite to ammonia. Under standard assay conditions catalysis proceeds without detected intermediates, and it has been assumed that this is also true in vivo. However, this report demonstrates that it is possible to trap a putative intermediate by controlling the electrochemical potential at which reduction takes place.