Cited by 403Metalloenzymes and iron-sulfur proteinsMicrobial Fuel Cells and BioremediationEnzyme Structure and Function

Enzymology and bioenergetics of respiratory nitrite ammonification

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Simon, Jörg·2002·FEMS Microbiology Reviews

Abstract

Nitrite is widely used by bacteria as an electron acceptor under anaerobic conditions. In respiratory nitrite ammonification an electrochemical proton potential across the membrane is generated by electron transport from a non-fermentable substrate like formate or H(2) to nitrite. The corresponding electron transport chain minimally comprises formate dehydrogenase or hydrogenase, a respiratory quinone and cytochrome c nitrite reductase. The catalytic subunit of the latter enzyme (NrfA) catalyzes nitrite reduction to ammonia without liberating intermediate products. This review focuses on recent progress that has been made in understanding the enzymology and bioenergetics of respiratory nitrite ammonification. High-resolution structures of NrfA proteins from different bacteria have been determined, and many nrf operons sequenced, leading to the prediction of electron transfer pathways from the quinone pool to NrfA. Furthermore, the coupled electron transport chain from formate to nitrite of Wolinella succinogenes has been reconstituted by incorporating the purified enzymes into liposomes. The NrfH protein of W. succinogenes, a tetraheme c-type cytochrome of the NapC/NirT family, forms a stable complex with NrfA in the membrane and serves in passing electrons from menaquinol to NrfA. Proteins similar to NrfH are predicted by open reading frames of several bacterial nrf gene clusters. In gamma-proteobacteria, however, NrfH is thought to be replaced by the nrfBCD gene products. The active site heme c group of NrfA proteins from different bacteria is covalently bound via the cysteine residues of a unique CXXCK motif. The lysine residue of this motif serves as an axial ligand to the heme iron thus replacing the conventional histidine residue. The attachment of the lysine-ligated heme group requires specialized proteins in W. succinogenes and Escherichia coli that are encoded by accessory nrf genes. The proteins predicted by these genes are unrelated in the two bacteria but similar to proteins of the respective conventional cytochrome c biogenesis systems.

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Crossref · 10.1111/j.1574-6976.2002.tb00616.x

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  • E. coli expresses two nitrite reductase enzymes (Nrf and Nir) that detoxify NO2− by rapidly converting it to ammonia through a six-electron reduction.

    “Alongside with transport E.coli expresses two nitrite reductase enzymes (Nrf and Nir) that detoxify NO2 - by rapidly converting it to ammonia through a six-electron reduction [18].”
  • Many enteric bacteria are capable of catalytic reduction of nitrate to N2 gas (denitrification) under anaerobic conditions, or to ammonia via two-step dissimilatory or assimilatory pathways.

    “Many enteric bacteria are also capable of catalytic reduction of nitrate to N2 gas (denitrification) under anaerobic conditions, or to ammonia via two-steps dissimilatory or assimilatory pathways [17,18].”

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Authors
Simon, J.
Affiliations
Goethe University Frankfurt (DE)
Corresponding author
Simon, Jörg
Venue
FEMS Microbiology Reviews
Published
2002-08
Volume
26
Issue
3
Pages
285-309
ISSN
  • 0168-6445 (ISSN-L)
  • 1574-6976
OpenAlex
W2033162758
Cited by
403
References
189
Citations by year
2026: 15 · 2025: 18 · 2024: 13 · 2023: 18 · 2022: 11 · 2021: 21 · 2020: 14 · 2019: 9 · 2018: 12 · 2017: 20 · 2016: 8 · 2015: 25 · 2014: 29 · 2013: 20 · 2012: 24
FWCI
11.07
Type
journal article
Language
en
Open access
Locations
  • FEMS Microbiology Reviews (publishedVersion)
  • PubMed (publishedVersion)
Funders
Deutsche Forschungsgemeinschaft (SFB 472)
Topics
  • Physical Sciences › Energy › Renewable Energy, Sustainability and the Environment › Metalloenzymes and iron-sulfur proteins
  • Physical Sciences › Environmental Science › Environmental Engineering › Microbial Fuel Cells and Bioremediation
  • Physical Sciences › Materials Science › Materials Chemistry › Enzyme Structure and Function
Keywords
cytochrome c nitrite reductase, nrfA, electron transport chain, heme c, heme attachment, Wolinella succinogenes, Escherichia coli, formate dehydrogenase, hydrogenase, respiratory quinones, cytochrome c biogenesis, bioenergetics
MeSH terms
Bacteria, Cytochrome c Group, Cytochromes c1, Multigene Family, Nitrate Reductases, Nitrites, Wolinella, Proteobacteria, Cytochromes a1

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