|Enzyme Name||Gene Culster||Enzyme Commission number||KEGG Orthology ID||
|Ammonia monooxygenase (AMO)||amoA
|188.8.131.52||K20934 K20933 K20932||Ammonia monooxygenase (AMO) catalyzes the oxidation of ammonia to hydroxylamine, the first reaction in the process of ammonia oxidation to nitrite.||Link|
|184.108.40.206||K10535||The enzyme catalyzes the oxidation of hydroxylamine to nitrite via an enzyme-bound nitroxyl intermediate. The main product is nitrite, in some cases nitric oxide is produced as well.||Link|
|220.127.116.11 18.104.22.168||K00370 K00371||The enzyme catalyzes the oxidation of nitrite to nitrate via an enzyme-bound nitroxyl intermediate. Under unaerobic
conditions the enzyme is a nitrate reductase, catalyzing the reverse reaction.
All known NOB oxidize nitrite by the enzyme NXR, which belongs to the type II group in the dimethyl sulfoxide reductase family of molybdopterin-cofactor-binding enzymes (Meincke et al., 1992; Lücker et al., 2010). NXR is membrane associated and contains an α subunit (NxrA) with the catalytic site and a β subunit (NxrB) that channels electrons derived from nitrite to downstream components of the respiratory chain (Kirstein and Bock, 1993). Most likely, a γ subunit (NxrC) functions as a membrane anchor that may be involved in electron transport (Lücker et al., 2010).