CHAPTER 6:Structure and Function of Nitric Oxide Reductases

Nitric oxide reductase (NOR) is a key enzyme in denitrification, since it contributes to the decomposition of highly cytotoxic NO, which is generated as an intermediate compound from NO2− catalysed by nitrite reductase. Bacterial NOR is a membrane-integrated enzyme that contains iron in its active site and catalyses the NO reduction as follows: 2NO + 2H+ + 2e− → N2O + H2O. First crystal structures of cytochrome c-dependent NOR from Pseudomonas aeruginosa and then that of quinol-dependent NOR from Geobacillus stearothermophilus were reported in 2010 and 2012, respectively. In this chapter, molecular and functional properties of NORs are described on the basis of these structures.