Editing Nitrification (section)

==Chemistry and enzymology==
Nitrification is a process of nitrogen compound [[redox|oxidation]] (effectively, loss of electrons from the [[nitrogen]] atom to the [[oxygen]] atoms), and is catalyzed step-wise by a series of enzymes.
:<chem>2NH4+ + 3O2 -> 2NO2- + 4H+ + 2H2O</chem> (''[[Nitrosomonas]]'', ''[[Comammox]]'')
:<chem>2NO2- + O2 -> 2NO3-</chem> (''[[Nitrobacter]]'', ''[[Nitrospira]]'', ''[[Comammox]]'')
OR
:<chem>NH3 + O2 -> NO2- + 3H+ + 2e-</chem>
:<chem>NO2- + H2O -> NO3- + 2H+ + 2e-</chem>
In ''[[Nitrosomonas europaea]]'', the first step of oxidation (ammonia to [[hydroxylamine]]) is carried out by the enzyme [[ammonia monooxygenase]] (AMO).

:<chem>NH3 + O2 + 2H+ -> NH2OH + H2O</chem>

The second step (hydroxylamine to nitrite) is catalyzed by two enzymes. [[Hydroxylamine Oxidoreductase|Hydroxylamine oxidoreductase]] (HAO), converts hydroxylamine to nitric oxide.<ref>{{cite journal | vauthors = Caranto JD, Lancaster KM | title = Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 114 | issue = 31 | pages = 8217–8222 | date = August 2017 | pmid = 28716929 | pmc = 5547625 | doi = 10.1073/pnas.1704504114 | bibcode = 2017PNAS..114.8217C | doi-access = free }}</ref>

:<chem>NH2OH -> NO + 3H+ + 3e-</chem>

Another currently unknown enzyme converts nitric oxide to nitrite.

The third step (nitrite to nitrate) is completed in a distinct organism.

:<chem>{nitrite} + acceptor <=> {nitrate} + reduced\ acceptor</chem>