Structural basis of denitrification

Denitrification represents an important part of the biogeochemical cycle of the essential element nitrogen. It constitutes the predominant pathway of the reductive dissimilation of nitrate in the environment. Via four enzymatic reactions, nitrate is transformed stepwise to nitrite (NO2-), nitric oxide (NO), and nitrous oxide (N2O), to finally yield dinitrogen gas (N-2). All steps within this metabolic pathway are catalyzed by complex multisite metalloenzymes with unique spectroscopic and structural features. In recent years, highresolution crystal structures have become available for these enzymes with the exception of the structure for NO reductase.