Thus, denitrifiers comprise the principal group of N2O producers, with roles played also by nitrifiers, methanotrophic bacteria, and fungi.

[3] Conversion of N2O into N2 is the last step of a complete nitrate denitrification process and is an autonomous form of respiration.

[5] Some denitrifiers do not have complete denitrification with end product N2O[6] Nitrous-oxide reductase is a homodimer that is located in the bacterial periplasm.

X-ray structures of the enzymes from Pseudomonas nautica and Paracoccus denitrificans have revealed that each subunit (MW=65 kDa) is organized into two domains.

The second domain comprises a 7-bladed propeller of β-sheets that contains the catalytic site called CuZ, which is a tetranuclear copper-sulfide cluster.