Photochemistry of nitric oxide adducts of water-soluble iron(III) porphyrin and ferrihemoproteins studied by nanosecond laser photolysis

Hoshino, Mikio; Ozawa, Kyoko; Seki, Hiroshi; Ford, Peter C.

doi:10.1021/ja00074a023

Cited by 298 publications

(325 citation statements)

References 12 publications

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“…4 Lower). 31 P NMR spectra did not reveal any changes in energy status (data not shown). However, we found significant differences in 1 H NMR spectra of WT hearts acquired within 4 min before, during, and after 1 M Bk stimulation (Fig.…”

Section: Resultsmentioning

confidence: 89%

Myoglobin: A scavenger of bioactive NO

Flogel¹

2001

Proceedings of the National Academy of Sciences

174

180

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Section: Resultsmentioning

confidence: 89%

Myoglobin: A scavenger of bioactive NO

Flogel¹

2001

Proceedings of the National Academy of Sciences

174

180

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“…[24][25][26] Ferrous hemoproteins typically exhibit a very high affinity for NO while the ferric forms bind NO with K d values in the micromolar range. [27][28][29][30] Because the concentration of NO during denitrification remains well below the micromolar range, it is assumed that the catalytic cycle of NO reductases is initiated by the binding of NO to an iron(II) in the reduced form of the enzyme.…”

Section: Spectroscopic Signatures Of Heme Iron-nitrosyl Complexesmentioning

confidence: 99%

Spectroscopic characterization of heme iron–nitrosyl species and their role in NO reductase mechanisms in diiron proteins

Moënne‐Loccoz

2007

Nat. Prod. Rep.

121

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Nitric oxide (NO) plays an important role in cell signalling and in the mammalian immune response to infection. On its own, NO is a relatively inert radical, and when it is used as a signalling molecule, its concentration remains within the picomolar range. However, at infection sites, the NO concentration can reach the micromolar range, and reactions with other radical species and transition metals lead to a broad toxicity. Under aerobic conditions, microorganisms cope with this nitrosative stress by oxidizing NO to nitrate (NO 3 − ). Microbial hemoglobins play an essential role in this NO-detoxifying process. Under anaerobic conditions, detoxification occurs via a 2-electron reduction of two NO molecules to N 2 O. In many bacteria and archaea, this NOreductase reaction is catalyzed by diiron proteins. Despite the importance of this reaction in providing microorganisms with a resistance to the mammalian immune response, its mechanism remains ill-defined. Because NO is an obligatory intermediate of the denitrification pathway, respiratory NO reductases also provide resistance to toxic concentrations of NO. This family of enzymes is the focus of this review. Respiratory NO reductases are integral membrane protein complexes that contain a norB subunit evolutionarily related to subunit I of cytochrome c oxidase (CcO). NorB anchors one high-spin heme b 3 and one non-heme iron known as Fe B , i.e., analogous to Cu B in CcO. A second group of diiron proteins with NO-reductase activity is comprised of the large family of soluble flavoprotein A found in strict and facultative anaerobic bacteria and archaea. These soluble detoxifying NO reductases contain a non-heme diiron cluster with a Fe-Fe distance of 3.4 Å and are only briefly mentioned here as a promising field of research. This article describes possible mechanisms of NO reduction to N 2 O in denitrifying NO-reductase (NOR) proteins and critically reviews recent experimental results. Relevant theoretical model calculations and spectroscopic studies of the NO-reductase reaction in heme/copper terminal oxidases are also overviewed.

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“…Two additional similar exchanges with Ar on the same sample did not change the EPR signals further. Previous reports have shown that Fe(III) heme-NO complexes will undergo photodissociation (41). The sample of Figure 6C was subjected to intense illumination with white light (300 W projection bulb) while in a room temperature water bath and additional exchanges with Ar during illumination.…”

Section: Uv-visible Spectroscopymentioning

confidence: 99%

Spectroscopic Characterization of the NO Adduct of Hydroxylamine Oxidoreductase

et al. 2002

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Hydroxylamine oxidoreductase (HAO) from the autotrophic nitrifying bacterium Nitrosomonas europaea catalyzes the oxidation of NH 2 OH to NO 2 -. The enzyme contains eight hemes per subunit which participate in catalysis and electron transport. NO is found to bind to the enzyme and inhibit electron flow to the acceptor protein, cytochrome c 554 . NO is found to oxidize either partially or fully reduced HAO, but NO will not reduce ferric HAO. Since NO can be reduced but not oxidized to product by HAO, NO is not considered to be a long-lived intermediate in the catalytic mechanism. Substrate oxidation occurs in the presence of bound NO or cyanide, suggesting a second interaction site for substrate with HAO and providing a means for recovery of the NO-inhibited form of the enzyme. Upon addition of NO to oxidized HAO, the integer-spin EPR signal from the active site vanishes, an IR band from NO appears at 1920 cm -1 , and a diamagnetic quadrupole iron doublet appears in Mössbauer spectroscopy with δ ) 0.06 mm/s and ∆Eq ) 2.1 mm/s. The NO stretching frequency and Mössbauer parameters are characteristic of an {FeNO} 6 heme complex. New Mössbauer data on ferric myoglobin-NO are also presented for comparison. The results indicate that NO binds to heme P460 and that the loss of the integer-spin EPR signal is due to the conversion of heme P460 to a diamagnetic S ) 0 state and concomitant loss of magnetic interaction with neighboring heme 6. In previous studies where the heme P460-heme 6 interaction was affected by substrate or cyanide binding, a signal attributable to heme 6 was not observable. In contrast, in this work, the NO-induced loss of the signal is accompanied by the appearance of a previously unobserved large g max (or HALS) low-spin EPR signal from heme 6.

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Photochemistry of nitric oxide adducts of water-soluble iron(III) porphyrin and ferrihemoproteins studied by nanosecond laser photolysis

Cited by 298 publications

References 12 publications

Myoglobin: A scavenger of bioactive NO

Myoglobin: A scavenger of bioactive NO

Spectroscopic characterization of heme iron–nitrosyl species and their role in NO reductase mechanisms in diiron proteins

Spectroscopic Characterization of the NO Adduct of Hydroxylamine Oxidoreductase

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