Chapter 8: The Enzymes and Bioenergetics of Bacterial Nitrate, Nitrite, Nitric Oxide and Nitrous Oxide Respiration

Summary

Respiratory reactions involving inorganic nitrogen species provide a rich variety of systems with which to study bacterial bioenergetics and biological chemistry. These respiratory reactions encompass the reduction of nitrate, nitrite, nitric oxide and nitrous oxide; in all cases catalysis involves redox chemistry that takes place at metal centers. These catalytic metal centers include mono-nuclear type II copper, c heme or d ₁ heme in nitrite reductases, the Mo-bis-molybdopterin guanine dinucleotide cofactor in nitrate reductases, a non heme Fe-heme Fe dincuclear center in nitric oxide reductases and a tetra-nuclear copper sulfide center in nitrous oxide reductase. Recent structures and new spectroscopic data for these enzymes have rapidly advanced our knowledge of the molecular and dynamic properties of the catalytic centers, as well as how electrons are transferred to them; models of catalysis can thus be proposed. Bioenergetic studies have also provided an understanding of the way in which these enzymes are coupled to energy-conserving electron transport pathways.