Metalloproteins with phenolate coordination

Que, Lawrence

doi:10.1016/0010-8545(83)85027-9

Cited by 116 publications

(35 citation statements)

References 161 publications

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“…[29] The other three vibrations are associated with phenolate C À O and ring deformation modes. [59,60] Similar assignments can be made for the 18 O-isotope-sensitive vibrations observed for the green chromophore from the 2,6-dimethylbenzoic acid experiments (Table 2). These results also proved that the phenolate oxygen originated from H 2 O 2 .…”

supporting

confidence: 53%

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H₂O₂

Makhlynets

Das

Taktak

et al. 2009

Chemistry A European J

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Regioselective hydroxylation of aromatic acids with hydrogen peroxide proceeds readily in the presence of iron(II) complexes with tetradentate aminopyridine ligands [Fe(II)(BPMEN)(CH(3)CN)(2)](ClO(4))(2) (1) and [Fe(II)(TPA)(CH(3)CN)(2)](OTf)(2) (2), where BPMEN=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-ethylenediamine, TPA=tris-(2-pyridylmethyl)amine. Two cis-sites, which are occupied by labile acetonitrile molecules in 1 and 2, are available for coordination of H(2)O(2) and substituted benzoic acids. The hydroxylation of the aromatic ring occurs exclusively in the vicinity of the anchoring carboxylate functional group: ortho-hydroxylation affords salicylates, whereas ipso-hydroxylation with concomitant decarboxylation yields phenolates. The outcome of the substituent-directed hydroxylation depends on the electronic properties and the position of substituents in the molecules of substrates: 3-substituted benzoic acids are preferentially ortho-hydroxylated, whereas 2- and, to a lesser extent, 4-substituted substrates tend to undergo ipso-hydroxylation/decarboxylation. These two pathways are not mutually exclusive and likely proceed via a common intermediate. Electron-withdrawing substituents on the aromatic ring of the carboxylic acids disfavor hydroxylation, indicating an electrophilic nature for the active oxidant. Complexes 1 and 2 exhibit similar reactivity patterns, but 1 generates a more powerful oxidant than 2. Spectroscopic and labeling studies exclude acylperoxoiron(III) and Fe(IV)=O species as potential reaction intermediates, but strongly indicate the involvement of an Fe(III)--OOH intermediate that undergoes intramolecular acid-promoted heterolytic O-O bond cleavage, producing a transient iron(V) oxidant.

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confidence: 53%

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H₂O₂

Makhlynets

Das

Taktak

et al. 2009

Chemistry A European J

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“…The iron(III)-phenolate moiety plays a very important role in biochemistry [1,2]. It occurs in many metalloproteins such transferrins, lactoferrins, purple phosphatases and catechol dioxygenases which contain tyrosinate as phenolate ligand.…”

Section: Introductionmentioning

confidence: 99%

Photoredox reactivity of iron(III) phenolates in aqueous solution induced by ligand-to-metal charge transfer excitation

Kunkely

Vogler

2003

Inorganic Chemistry Communications

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“…co-ordination in AMO is further supported by the finding that Fe 3? is not reduced by ascorbate/ MPMS or DT/MPMS which is a typical feature of iron-tyrosinate proteins (Que 1983;Que and Jo 1996).…”

Section: Resultsmentioning

confidence: 99%

Electron paramagnetic studies of the copper and iron containing soluble ammonia monooxygenase from Nitrosomonas europaea

2010

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Soluble ammonia monooxygenase (AMO) from Nitrosomonas europaea was purified to homogeneity and metals in the active sites of the enzyme (Cu, Fe) were analyzed by electron paramagnetic resonance (EPR) spectroscopy. EPR spectra were obtained for a type 2 Cu(II) site with g(parallel) = 2.24, A(parallel) = 18.4 mT and g(perpendicular) = 2.057 as well as for heme and non heme iron present in purified soluble AMO from N. europaea. A second type 2 Cu(II) EPR signal with g(parallel) = 2.29, A(parallel) = 16.1 mT and g(perpendicular) = 2.03 appeared in the spectrum of the ferricyanide oxidized enzyme and was attributed to oxidation of cuprous sites. Comparison of EPR-detectable Cu(2+) with total copper determined by inductively coupled plasma-mass spectrometry (ICP-MS) suggests that there are six paramagnetic Cu(2+) and three diamagnetic Cu(1+) per heterotrimeric soluble AMO (two paramagnetic and one diamagnetic Cu per alphabetagamma-protomer). A trigonal EPR signal at g = 6.01, caused by a high-spin iron, indicative for cytochrome bound iron, and a rhombic signal at g = 4.31, characteristic of specifically bound Fe(3+) was detectable. The binding of nitric oxide in the presence of reductant resulted in a ferrous S = 3/2 signal, characteristic of a ferrous nitrosyl complex. Inactivation of soluble AMO with acetylene did neither diminish the ferrous signal nor the intensity of the Cu(2+)-EPR signal.

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Metalloproteins with phenolate coordination

Cited by 116 publications

References 161 publications

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H₂O₂

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H₂O₂

Photoredox reactivity of iron(III) phenolates in aqueous solution induced by ligand-to-metal charge transfer excitation

Electron paramagnetic studies of the copper and iron containing soluble ammonia monooxygenase from Nitrosomonas europaea

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Metalloproteins with phenolate coordination

Cited by 116 publications

References 161 publications

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H2O2

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H2O2

Photoredox reactivity of iron(III) phenolates in aqueous solution induced by ligand-to-metal charge transfer excitation

Electron paramagnetic studies of the copper and iron containing soluble ammonia monooxygenase from Nitrosomonas europaea

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Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H₂O₂

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H₂O₂