Model compound studies related to peroxidases. Mechanisms of reactions of hemins with peracids

Traylor, T. G.; Lee, William A.; Stynes, Dennis V.

doi:10.1021/ja00315a050

Cited by 129 publications

(70 citation statements)

References 9 publications

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“…All the reactions were performed in CH 2 Cl 2 at 0 1C. Initial rates of the formation of TBP free radical 4 was measured by the increase of the peak at 630 nm (e ¼ 400 M À 1 cm À 1 ) 32 before the conversion reached to 30%. The concentration of 1 or 3 was maintained as constant while the other one was changed.…”

Section: Discussionmentioning

confidence: 99%

“…By presenting a stable phenoxy radical the TBPH was able to trap a high valent intermediate 32 . Figure 2b shows .…”

Section: Rapid High Valent Intermediate Trapping Reactionsmentioning

confidence: 99%

“…Peroxyacids 26,[32][33][34][35] , hydroperoxides [36][37][38][39] or inorganic salts [40][41][42][43][44][45] were generally employed as terminal oxidants in mechanistic studies, and the reactions were always performed in water or mixed solvents (such as CH 3 OH/H 2 O or CH 3 CN/H 2 O). In fact, PhIO is often mechanistically cleaner than these alternatives 46 .…”

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confidence: 99%

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Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Guo

Dong

et al. 2012

Nat Commun

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Different metalloporphyrin model compounds have been synthesized to study the mechanisms of cytochrome P450s with various terminal oxidants, and numerous intermediates have been reported. However, the detailed mechanism of the oxygen atom transfer from iodosylarene to the substrates remains unclear. Here we report the direct ultraviolet-visible spectroscopic observation of the soluble iodosylarene-manganese porphyrin adduct following catalytic oxidation using 2,4,6-tri-tert-butylphenol as the reductant. When the reductant is changed to cisstilbene, the rate-determining step also changes. Both the iodosylarene-manganese porphyrin adduct and [(porphyrin)Mn(V) ¼ O] species may be simultaneously observed. In the absence of reductant, the adduct of iodosylarene with sterically hindered [Mn(meso-tetrakis(2,6-dichlorophenyl)porphinato)Cl] is immediately formed, and smoothly converted into a highvalent [(porpyrinato)Mn ¼ O]. Electrospray ionization mass spectrometry analysis of the reaction further confirms the transformation between these species. This study provides an insight into the mechanism of oxygen transfer within the haem-containing enzymatic systems.

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Section: Discussionmentioning

confidence: 99%

“…By presenting a stable phenoxy radical the TBPH was able to trap a high valent intermediate 32 . Figure 2b shows .…”

Section: Rapid High Valent Intermediate Trapping Reactionsmentioning

confidence: 99%

mentioning

confidence: 99%

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Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Guo

Dong

et al. 2012

Nat Commun

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“…With the aim of studying these effects, several chelated iron-porphyrin model systems have been synthesized, containing an appended imidazole residue which can intramolecularly bind to the iron center [8][9][10][11][12][13][14][15][16][17][18][19]. A different approach involves the use of heme-peptide complexes (called microperoxidases) obtained from the proteolysis of horse heart cytochrome c [20,21].…”

Section: Introductionmentioning

confidence: 99%

pH-dependent redox and CO binding properties of chelated protoheme-l-histidine and protoheme-glycyl-l-histidine complexes

et al. 2005

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The pH dependence of redox properties, spectroscopic features and CO binding kinetics for the chelated protohemin-6(7)-L-histidine methyl ester (heme-H) and the chelated protohemin-6(7)-glycyl-L-histidine methyl ester (heme-GH) systems has been investigated between pH 2.0 and 12.0. The two heme systems appear to be modulated by four protonating groups, tentatively identified as coordinated H 2 O, one of heme's propionates, Ne of the coordinating imidazole, and the carboxylate of the histidine residue upon hydrolysis of the methyl ester group (in acid medium). The pK a values are different for the two hemes, thus reflecting structural differences. In particular, the different strain at the Fe-N e bond, related to the different length of the coordinating arm, results in a dramatic alteration of the bond strength, which is much smaller in heme-H than in heme-GH. It leads to a variation in the variation of the pKa for the protonation of the N e of the axial imidazole as well as in the proton-linked behavior of the other protonating groups, envisaging a cross-talk communication mechanism among different groups of the heme, which can be operative and relevant also in the presence of the protein matrix.

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“…Peroxidase activity in biological systems was first reported in the 19th century [13] and a reaction mechanism was proposed for these enzymes (Scheme 1). It has been shown that compound 0 is formed quickly but the complicated O-O cleavage is the limiting step of the peroxidase cycle [14]. This is a major contribution for the decrease of the rate in the second kinetic trace.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes

et al. 2016

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Abstract:The spectroscopic and kinetic characterization of two intermediates from the H 2 O 2 oxidation of three dimethyl ester [(proto), (meso), (deuteroporphyrinato) (picdien)]Fe(III) complexes ([FePPPic], [FeMPPic] and [FeDPPic], respectively) pinch-porphyrin peroxidase enzyme models, with s = 5/2 and 3/2 Fe(III) quantum mixed spin (qms) ground states is described herein. The kinetic study by UV/Vis at λ max = 465 nm showed two different types of kinetics during the oxidation process in the guaiacol test for peroxidases (1-3 + guaiacol + H 2 O 2 Ñ oxidation guaiacol products). The first intermediate was observed during the first 24 s of the reaction. When the reaction conditions were changed to higher concentration of pinch-porphyrins and hydrogen peroxide only one type of kinetics was observed. Next, the reaction was performed only between pinch-porphyrins-Fe(III) and H 2 O 2 , resulting in only two types of kinetics that were developed during the first 0-4 s. After this time a self-oxidation process was observed. Our hypotheses state that the formation of the π-cation radicals, reaction intermediates of the pinch-porphyrin-Fe(III) family with the ligand picdien [N,N'-bis-pyridin-2-ylmethyl-propane-1,3-diamine], occurred with unique kinetics that are different from the overall process and was involved in the oxidation pathway. UV-Vis, 1 H-NMR and ESR spectra confirmed the formation of such intermediates. The results in this paper highlight the link between different spectroscopic techniques that positively depict the kinetic traits of artificial compounds with enzyme-like activity.

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Model compound studies related to peroxidases. Mechanisms of reactions of hemins with peracids

Cited by 129 publications

References 9 publications

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

pH-dependent redox and CO binding properties of chelated protoheme-l-histidine and protoheme-glycyl-l-histidine complexes

Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes

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