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Updated: Jul 11, 2026

Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds
Published on: February 16, 2022
Stable copper-nitrosyl formation by nitrite reductase in either oxidation state
Elitza I Tocheva1, Federico I Rosell, A Grant Mauk
1Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver BC, V6T 1Z3, Canada.
Researchers characterized copper-nitrosyl intermediates in nitrite reductase (NiR) using X-ray crystallography. They identified a stable Cu(II)-NO- species, offering new insights into bacterial denitrification mechanisms.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Nitrite reductase (NiR) is crucial for bacterial denitrification, reducing nitrite to nitric oxide.
- A copper-nitrosyl intermediate (Cu(I)-NO+) is proposed in the NiR catalytic cycle but remains poorly characterized.
Purpose of the Study:
- To structurally characterize copper-nitrosyl complexes in Alcaligenes faecalis NiR (AfNiR).
- To elucidate the role of copper sites and specific residues in intermediate formation.
Main Methods:
- X-ray crystallography of wild-type and mutant AfNiR crystals exposed to nitric oxide (NO).
- Electron paramagnetic resonance (EPR) spectroscopy of NiR-NO complexes.
Main Results:
- Observed a reverse reaction forming nitrite in wild-type NiR crystals.
- Identified side-on NO binding to the type 2 copper site in a type 1 copper mutant (H145A).
- Characterized stable Cu(II)-NO- species via EPR, distinct from the proposed Cu(I)-NO+ intermediate.
Conclusions:
- The study reveals stable copper-nitrosyl species, challenging the proposed Cu(I)-NO+ intermediate.
- Structural and spectroscopic data provide a refined understanding of the NiR catalytic mechanism and denitrification.
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