Ammonia monooxygenase explained

Ammonia monooxygenase
Ec Number:	1.14.99.39

Ammonia monooxygenase (AMO) is an enzyme,^{[1] [2] [3] [4] [5] [6] [7] [8] [9]} which catalyses the following chemical reaction

ammonia + AH₂ + O₂

\rightleftharpoons NH₂OH + A + H₂O

Ammonia monooxygenase contains copper and possibly nonheme iron. AMO is the first enzyme in ammonia oxidation. Aerobic oxidation of ammonia to hydroxylamine via AMO is an endergonic reaction. So, all aerobic ammonia oxidizing organisms conserve energy by further oxidizing hydroxylamine. It was believed that aerobic ammonia-oxidizing bacteria oxidize hydroxylamine to nitrite using octahaem hydroxylamine oxidoreductase (HAO). Recently, it was shown that the product of HAO is not nitrite but nitric oxide, which is further oxidized to nitrite by an unknown enzyme.

Notes and References

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7. Arp DJ, Sayavedra-Soto LA, Hommes NG . Molecular biology and biochemistry of ammonia oxidation by Nitrosomonas europaea . Archives of Microbiology . 178 . 4 . 250–5 . October 2002 . 12209257 . 10.1007/s00203-002-0452-0 .
8. Gilch S, Meyer O, Schmidt I . A soluble form of ammonia monooxygenase in Nitrosomonas europaea . Biological Chemistry . 390 . 9 . 863–73 . September 2009 . 19453274 . 10.1515/BC.2009.085 .
9. Rasche ME, Hicks RE, Hyman MR, Arp DJ . Oxidation of monohalogenated ethanes and n-chlorinated alkanes by whole cells of Nitrosomonas europaea . Journal of Bacteriology . 172 . 9 . 5368–73 . September 1990 . 10.1128/jb.172.9.5368-5373.1990 . 2394686 . 213201 .