4n4j
Kuenenia stuttgartiensis hydroxylamine oxidoreductase
Structural highlights
FunctionHAO_KUEST Catalyzes the oxidation of hydroxylamine to nitric oxide with cytochrome c acting as an electron acceptor (PubMed:21964329, PubMed:24302732). Does not oxidize hydroxylamine to nitrite (PubMed:24302732). Also able to catalyze the four-electron oxidation of hydrazine to N(2) in vitro with reduced efficiency; however, this reaction is probably not physiological (PubMed:21964329, PubMed:24302732).[1] [2] Publication Abstract from PubMedNitric oxide (NO) is an important molecule in all domains of life with significant biological functions in both pro- and eukaryotes. Anaerobic ammonium-oxidizing (anammox) bacteria that contribute substantially to the release of fixed nitrogen into the atmosphere use the oxidizing power of NO to activate inert ammonium into hydrazine (N2H4). Here, we describe an enzyme from the anammox bacterium Kuenenia stuttgartiensis that uses a novel pathway to make NO from hydroxylamine. This new enzyme is related to octaheme hydroxylamine oxidoreductase (HAO), a key protein in aerobic ammonium-oxidizing bacteria. By a multiphasic approach including the determination of the crystal structure of the K. stuttgartiensis enzyme at 1.8Angstrom resolution and refinement and reassessment of the HAO structure from Nitrosomonas europaea, both in the presence and absence of their substrates, we propose a model for NO formation by the K. stuttgartiensis enzyme. Our results expand the understanding of the functions that the widespread family of octaheme proteins have. Structural basis of biological NO generation by octaheme oxidoreductases.,Maalcke WJ, Dietl A, Marritt SJ, Butt JN, Jetten MS, Keltjens JT, Barends TR, Kartal B J Biol Chem. 2013 Dec 3. PMID:24302732[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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