2004 Volume 44 Issue 4 Pages 155-160
From chemical point of view, the NO reduction to N2O is one of the most attractive subjects, since it contains the N-O bond cleavage and N-N bond formation with aid of two electrons and two protons. Nitric oxide reductase (NOR) is a key enzyme for this reaction in biological denitrification processes. Two types of NORs have been isolated from some microorganisms and characterized; one is a soluble cytochrome P450-type enzyme from fungi, whereas the other is a membrane-bound cytochrome bc-type complex from denitrifying bacteria. These NORs effectively catalyze the NO reduction in a quite different mechanism. Here we summarize the current results in the mechanistic study of NO reduction reaction conducted by each enzyme, and discuss their molecular mechanism based on their structural and functional information.
