Biomimetic NOx Reductions by Heme Models and Proteins

Blair, Emek; Sulc, Filip; Farmer, Patrick J.

doi:10.1007/0-387-28430-3_4

Cited by 3 publications

(5 citation statements)

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“…1 The six-electron reduction of nitrite to ammonia can be driven by a single enzyme, as in the assimilatory nitrite reductases, or can occur stepwise via the dissimilatory enzymes, which take nitrite to NO, N 2 O and N 2 . Heme nitroxyl intermediates have been postulated in these NO x reductions, as indicated by the dotted line in Scheme 1.…”

Section: Hno-heme Adductsmentioning

confidence: 99%

“…Interest in HNO in the Farmer laboratory originated from efforts to model reductive heme-based catalysis involved in the global nitrogen cycle (Scheme 1). 1 The six-electron reduction of nitrite to ammonia can be driven by a single enzyme, as in assimilatory nitrite reductases, or can occur stepwise via dissimilatory enzymes, which take nitrite to nitric oxide (NO), N 2 O, and N 2 . Heme nitroxyl intermediates have been postulated in these NO x reductions, as indicated by the dotted line in Scheme 1.…”

Section: Hno-heme Adductsmentioning

confidence: 99%

“…11 In a recent series of papers, we have shown that an HNO adduct of ferrous myoglobin (HNO-Fe II Mb) can be formed by the reduction of NO-Fe II Mb or by the trapping of free HNO by deoxymyoglobin (Fe II Mb). 15,16 The HNO-Fe II Mb adduct is relatively stable, and as a unique model for heme nitroxyl intermediates, it has been structurally characterized by 1 H NMR, 17 resonance Raman, and X-ray absorption spectroscopy/X-ray absorption near-edge structure analysis. 18 The 1 H NMR spectrum is particularly diagnostic, with characteristic signals for HNO at 14.9 ppm and for the methyl group of Val68 at -2.5 ppm.…”

Section: Hno-heme Adductsmentioning

confidence: 99%

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Reactions of HNO with Heme Proteins: New Routes to HNO−Heme Complexes and Insight into Physiological Effects

et al. 2010

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The formation and interconversion of nitrogen oxides has been of interest in numerous contexts for decades. Early studies focused on gas-phase reactions, particularly with regard to industrial and atmospheric environments, and on nitrogen fixation. Additionally, investigation of the coordination chemistry of nitric oxide (NO) with hemoglobin dates back nearly a century. With the discovery in the early 1980s that NO is biosynthesized as a molecular signaling agent, the literature has been focused on the biological effects of nitrogen oxides, but the original concerns remain relevant. For instance, hemoglobin has long been known to react with nitrite, but this reductase activity has recently been considered to be important to produce NO under hypoxic conditions. The association of nitrosyl hydride (HNO; also commonly referred to as nitroxyl) with heme proteins can also produce NO by reductive nitrosylation. Furthermore, HNO is considered to be an intermediate in bacterial denitrification, but conclusive identification has been elusive. The authors of this article have approached the bioinorganic chemistry of HNO from different perspectives, which have converged because heme proteins are important biological targets of HNO.

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Section: Hno-heme Adductsmentioning

confidence: 99%

Section: Hno-heme Adductsmentioning

confidence: 99%

Section: Hno-heme Adductsmentioning

confidence: 99%

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Reactions of HNO with Heme Proteins: New Routes to HNO−Heme Complexes and Insight into Physiological Effects

et al. 2010

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“…Yet, none of these authors could find an explanation for the fact. Alternative reactions routes for the electrocatalytic reduction of NO x compounds by heme models and proteins have been also proposed and were broadly reviewed by Blair and co-workers [ 55 ].…”

Section: Amperometric And/or Voltammetric Biosensorsmentioning

confidence: 99%

Nitrite Biosensing via Selective Enzymes—A Long but Promising Route

Almeida

Serra

Silveira

et al. 2010

Sensors

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The last decades have witnessed a steady increase of the social and political awareness for the need of monitoring and controlling environmental and industrial processes. In the case of nitrite ion, due to its potential toxicity for human health, the European Union has recently implemented a number of rules to restrict its level in drinking waters and food products. Although several analytical protocols have been proposed for nitrite quantification, none of them enable a reliable and quick analysis of complex samples. An alternative approach relies on the construction of biosensing devices using stable enzymes, with both high activity and specificity for nitrite. In this paper we review the current state-of-the-art in the field of electrochemical and optical biosensors using nitrite reducing enzymes as biorecognition elements and discuss the opportunities and challenges in this emerging market.

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“…An HNO-Mn II species with a d 5 electronic configuration is unprecedented, as all isolable HNO-metal complexes are diamagnetic with low-spin d 6 metal ions. But there exists precedence for reduction of a metal-bound HNO in the catalytic cycles of various nitrite reductases (52)(53)(54). The singly reduced form of HNO, the aminoxyl radical anion (HNO − ), is generated by photolysis of the stable HNO adduct of deoxymyoglobin (55); and published theoretical calculations suggest that a protoncoupled oxidation HNO∕Fe II to H 2 NO∕Fe III is enthalpically favorable (56,57).…”

Section: Discussionmentioning

confidence: 99%

Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase

Kumar

Zapata

Ramirez

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Quercetin dioxygenase (QDO) catalyzes the oxidation of the flavonol quercetin with dioxygen, cleaving the central heterocyclic ring and releasing CO. The QDO from Bacillus subtilis is unusual in that it has been shown to be active with several divalent metal cofactors such as Fe, Mn, and Co. Previous comparison of the catalytic activities suggest that Mn(II) is the preferred cofactor for this enzyme. We herein report the unprecedented substitution of nitrosyl hydride (HNO) for dioxygen in the activity of Mn-QDO, resulting in the incorporation of both N and O atoms into the product. Turnover is demonstrated by consumption of quercetin and other related substrates under anaerobic conditions in the presence of HNO-releasing compounds and the enzyme. As with dioxygenase activity, a nonenzymatic base-catalyzed reaction of quercetin with HNO is observed above pH 7, but no enhancement of this basal reactivity is found upon addition of divalent metal salts. Unique and regioselective N-containing products ( 14 N∕ 15 N) have been characterized by MS analysis for both the enzymatic and nonenzymatic reactions. Of the several metallo-QDO enzymes examined for nitroxygenase activity under anaerobic condition, only the Mn(II) is active; the Fe(II) and Co(II) substituted enzymes show little or no activity. This result represents an enzymatic catalysis which we denote nitroxygenase activity; the unique reactivity of the Mn-QDO suggests a metalmediated electron transfer mechanism rather than metal activation of the substrate's inherent base-catalyzed reactivity.nitroxyl | quercetinase D ioxygenases are enzymes that incorporate both atoms of dioxygen into a targeted substrate, e.g., the enzyme catechol 1,2-dioxygenase cleaves the C-C bond between catechol's two hydroxyl groups forming the dicarboxylate cis,cis-muconic acid (1). Although highly divergent, there are two broadly defined classes of nonheme dioxygenases: those that directly bind dioxygen at the metal center or those in which dioxygen binds to the substrate that has been activated by interaction with the metal center (2). Such questions also apply to quercetin dioxygenase (QDO), which catalyzes the oxidation of the flavonol quercetin (1) with dioxygen ( Fig. 1). During turnover, QDO cleaves the central heterocyclic ring of quercetin, releasing CO, and yielding the corresponding depside. The QDO from Bacillus subtilis is unusual in that it has been shown to be active with several divalent metal cofactors such as Cu, Fe, Mn, and Co. Comparison of the catalytic activities suggest that Mn(II) is the preferred cofactor for this enzyme (3).The simple molecule nitrosyl hydride (HNO) is the singly reduced and protonated form of nitric oxide, NO. HNO has garnered much interest because it demonstrates a physiological reactivity distinctly different from its congener nitric oxide (4, 5). In a series of papers, we have reported the preparation and characterization of the HNO adduct of myoglobin (HNO-Mb) by reduction of 7) and by trapping of free HNO by deoxymyoglobin (Mb-Fe II ) (8)...

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Biomimetic NOx Reductions by Heme Models and Proteins

Cited by 3 publications

References 0 publications

Reactions of HNO with Heme Proteins: New Routes to HNO−Heme Complexes and Insight into Physiological Effects

Reactions of HNO with Heme Proteins: New Routes to HNO−Heme Complexes and Insight into Physiological Effects

Nitrite Biosensing via Selective Enzymes—A Long but Promising Route

Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase

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