Yoshitsugu Shiro

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.

Molecular Mechanism of Metal-Containing Oxygenases

Over a past few years, we have determined crystal structures of several metal-containing oxygenases including indoleamin-2, 3-dioxygenase and some P450s which have interesting chemistry and play important roles in metabolism. Molecular mechanisms of these oxygenases are discussed based on the crystal structures.