Cytochrome C Nitrite Reductase and Nitrous Oxide Reductase: Two Metallo Enzymes of the Nitrogen Cycle with Novel Metal Sites

Within the biogeochemical nitrogen cycle NxOv compounds function as electron acceptors of anaerobic respiratory chains (Stouthamer, 1988). Prokaryotes carry out their energy conservation during reduction of these nitrogen compounds, such as nitrate, nitrite, nitric oxide (nitrogen monoxide, NO), and nitrous oxide (dinitrogen monoxide, N2O ), and use complex transition metal enzymes for the transformation of the nitrogen oxides (Kroneck and Zumft, 1990; Zumft and Kroneck, 1990; Zumft, 1992).