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Publication Abstract from PubMed

Nitrifier denitrification is the conversion of nitrite to nitrous oxide by ammonia oxidizing organisms. This process, which is distinct from denitrification, is active under aerobic conditions in the model nitrifier Nitrosomonas europaea. The central enzyme of the nitrifier dentrification pathway is a copper nitrite reductase (CuNIR). To understand how a CuNIR, typically inactivated by oxygen, functions in this pathway, the enzyme isolated directly from N. europaea (NeNIR) was biochemically and structurally characterized. NeNIR reduces nitrite at a similar rate to other CuNIRs, but appears to be oxygen tolerant. Crystal structures of oxidized and reduced NeNIR reveal a substrate channel to the active site that is much more restricted than channels in typical CuNIRs. In addition, there is a second fully hydrated channel leading to the active site that likely acts a water exit pathway. The structure is minimally affected by changes in pH. Taken together, these findings provide insight into the molecular basis for NeNIR oxygen tolerance.

Characterization of a Nitrite Reductase Involved in Nitrifier Denitrification.,Lawton TJ, Bowen KE, Sayavedra-Soto LA, Arp DJ, Rosenzweig AC J Biol Chem. 2013 Jul 15. PMID:23857587^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.