Abstract:
Nitrite reductase (NiR) is a key enzyme in the natural nitrogen cycle that catalyzes the reduction of nitrite. Cu-NiR and cd
1-NiR, which are encoded by the
nirK and
nirS genes, respectively, are rate-limiting enzymes in denitrification. Although they have similar functions, their structures and cofactors are different. In addition, they exhibit different responses to different environmental gradients. The structural characteristics, microbial population distribution, and detection techniques of these two enzymes are reviewed in this report. Furthermore, the environmental factors that determine the expression and activity of the
nirS and
nirK genes are examined. Finally, future research directions are proposed.