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Title: Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase

Ammonia (NH 3)-oxidizing bacteria (AOB) emit substantial amounts of nitric oxide (NO) and nitrous oxide (N 2O), both of which contribute to the harmful environmental side effects of large-scale agriculture. The currently accepted model for AOB metabolism involves NH 3 oxidation to nitrite (NO 2 ) via a single obligate intermediate, hydroxylamine (NH 2OH). Within this model, the multiheme enzyme hydroxylamine oxidoreductase (HAO) catalyzes the four-electron oxidation of NH 2OH to NO 2 . In this paper, we provide evidence that HAO oxidizes NH 2OH by only three electrons to NO under both anaerobic and aerobic conditions. NO 2 observed in HAO activity assays is a nonenzymatic product resulting from the oxidation of NO by O 2 under aerobic conditions. Finally, our present study implies that aerobic NH 3 oxidation by AOB occurs via two obligate intermediates, NH 2OH and NO, necessitating a mediator of the third enzymatic step.
Authors:
 [1] ; ORCiD logo [1]
  1. Cornell Univ., Ithaca, NY (United States). Dept. of Chemistry and Chemical Biology
Publication Date:
Grant/Contract Number:
SC0013997
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 31; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Cornell Univ., Ithaca, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; nitrification; nitric oxide; enzymology; bioinorganic chemistry
OSTI Identifier:
1371603
Alternate Identifier(s):
OSTI ID: 1465961

Caranto, Jonathan D., and Lancaster, Kyle M.. Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase. United States: N. p., Web. doi:10.1073/pnas.1704504114.
Caranto, Jonathan D., & Lancaster, Kyle M.. Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase. United States. doi:10.1073/pnas.1704504114.
Caranto, Jonathan D., and Lancaster, Kyle M.. 2017. "Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase". United States. doi:10.1073/pnas.1704504114.
@article{osti_1371603,
title = {Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase},
author = {Caranto, Jonathan D. and Lancaster, Kyle M.},
abstractNote = {Ammonia (NH3)-oxidizing bacteria (AOB) emit substantial amounts of nitric oxide (NO) and nitrous oxide (N2O), both of which contribute to the harmful environmental side effects of large-scale agriculture. The currently accepted model for AOB metabolism involves NH3 oxidation to nitrite (NO2–) via a single obligate intermediate, hydroxylamine (NH2OH). Within this model, the multiheme enzyme hydroxylamine oxidoreductase (HAO) catalyzes the four-electron oxidation of NH2OH to NO2–. In this paper, we provide evidence that HAO oxidizes NH2OH by only three electrons to NO under both anaerobic and aerobic conditions. NO2– observed in HAO activity assays is a nonenzymatic product resulting from the oxidation of NO by O2 under aerobic conditions. Finally, our present study implies that aerobic NH3 oxidation by AOB occurs via two obligate intermediates, NH2OH and NO, necessitating a mediator of the third enzymatic step.},
doi = {10.1073/pnas.1704504114},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 31,
volume = 114,
place = {United States},
year = {2017},
month = {7}
}