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Issue 37, 2007
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Flavo-diiron enzymes: nitric oxide or dioxygen reductases?

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Abstract

Flavo-diiron enzymes are among the most recently recognized sub-class of non-heme diiron proteins. The active sites of flavo-diiron enzymes consist of a unique juxtaposition of a flavincofactor and a histidine, glutamate, aspartate-ligated, solvent-bridged diiron site. Flavo-diiron enzymes were initially thought to function as scavenging dioxygen reductases (s-O2Rs), based on their ability to catalyze the reduction of dioxygen to water, thus protecting air-sensitive bacteria and archaea against “oxidative stress”. However, genetic and biochemical evidence strongly suggests that, at least in some bacteria, flavo-diiron enzymes function as scavenging nitric oxide reductases (s-NORs), catalyzing the reduction of nitric oxide to nitrous oxide, thus, protecting against “nitrosative stress” under anaerobic growth conditions. Key unsettled questions include: should flavo-diiron enzymes be divided into s-NOR and s-O2R categories, and, if so, what features of the active sites distinguish the two activities? If not, how does the active site accommodate and optimize the relative levels of these activities? Systematic investigations of the structures and catalytic mechanisms of several flavo-diiron enzymes constitute an approach to answer these questions. The current state of knowledge and progress toward this end is reviewed here.

Graphical abstract: Flavo-diiron enzymes: nitric oxide or dioxygen reductases?

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Publication details

The article was received on 02 Jul 2007, accepted on 06 Aug 2007 and first published on 15 Aug 2007


Article type: Perspective
DOI: 10.1039/B710047G
Citation: Dalton Trans., 2007,0, 4115-4121
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    Flavo-diiron enzymes: nitric oxide or dioxygen reductases?

    D. M. Kurtz, Jr., Dalton Trans., 2007, 0, 4115
    DOI: 10.1039/B710047G

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