Nitroalkane Oxidation Mechanisms in Flavoprotein Enzymes

Flavoprotein enzymes that catalyse the oxidation of nitroalkanes play a central role in the biochemical transformation of environmental pollutants and in metabolic pathways across diverse organisms. These enzymes typically employ a flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) cofactor to activate molecular oxygen and facilitate the conversion of primary and secondary nitroalkanes into carbonyl compounds, nitrite and, in some cases, hydrogen peroxide. The catalytic cycle generally proceeds via substrate-assisted reduction of the flavin to a semiquinone or hydroquinone state, followed by reaction with oxygen to generate a flavin peroxide intermediate. Subsequent electron transfer and proton shuttling lead to cleavage of the nitro group and release of the oxidised product. Key mechanistic features include the deprotonation of the nitroalkane to form a nitronate anion, stabilisation of radical intermediates by the flavin semiquinone, and the involvement of active-site residues as proton donors or bases. Structural studies have revealed conserved motifs for flavin binding and have identified catalytic residues such as a histidine that functions as a general base. Together, these insights underpin the design of biocatalysts for green chemistry and guide efforts to engineer enhanced pollutant-degrading enzymes.

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Nitroalkane Oxidation Mechanisms in Flavoprotein Enzymes publication trend

The graph below shows the total number of articles in nitroalkane oxidation mechanisms in flavoprotein enzymes across all publications each year (not limited to Nature Index journals).

Technical terms

Flavoprotein: An enzyme that contains a flavin cofactor (FMN or FAD) which mediates redox reactions.

Nitroalkane: An organic molecule in which one or more hydrogen atoms on an alkane are replaced by a nitro (–NO2) group.

Flavin semiquinone: A one-electron reduced, radical form of flavin that serves as a catalytic intermediate in oxidation reactions.

Nitronate: The conjugate base of a nitroalkane, formed by deprotonation at the α-carbon, and often the true substrate for monooxygenase enzymes.

Oxidase: An enzyme that catalyses the transfer of electrons from a substrate to molecular oxygen, typically generating peroxide or water.

References

1. A Novel Cold-Adapted Nitronate Monooxygenase from Psychrobacter sp. ANT206: Identification, Characterization and Degradation of 2-Nitropropane at Low Temperature. Microorganisms (2024).
2. Involvement of a Flavosemiquinone in the Enzymatic Oxidation of Nitroalkanes Catalyzed by 2-Nitropropane Dioxygenase*. Journal of Biological Chemistry (2004).
3. Crystal Structure of 2-Nitropropane Dioxygenase Complexed with FMN and Substrate IDENTIFICATION OF THE CATALYTIC BASE* * This work was supported by the Korea Ministry of Science and Technology (Grant NRL-2001). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S1-S7 and Tables S1 and S2.. Journal of Biological Chemistry (2006).