Hemepeptide models for hemoproteins: the behavior of -acetylmicroperoxidase-11 in aqueous solution

Marques, Helder M.; Perry, Christopher B.

doi:10.1016/s0162-0134(99)00100-2

Cited by 48 publications

(72 citation statements)

References 32 publications

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“…In the case of 25% acetonitrile, coordination of the 6 th axial ligand position of the haem iron by the solvent is apparent, with a red-shift in the position of the Soret 35 peak (399 to 411 nm), a prominent shoulder appearing on the Soret band around 360 nm, and the presence of the Q v band at 533 nm. These features are consistent with the formation of a 6-coordinate, low-spin haem species 56 which is likely to inhibit peroxide binding to the MP-11 and lower the catalytic activity. For 5% THF, a red- 40 shift in peak position and significant reduction in intensity (80%) was noted for the Soret band.…”

Section: Kinetics Of Sulphide Oxidationsupporting

confidence: 73%

The effect of solvent on the catalytic properties of microperoxidase-11

O’Reilly

Magner

2011

Phys. Chem. Chem. Phys.

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The effect of a range of solvents on the catalytic oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide by MP-11 and by a cyclodextrin derivative of MP-11 was examined. The addition of low concentrations of alcohols enhanced the initial rate of sulfoxidation rate, most likely due to dispersion of MP-11 aggregates. Higher alcohol concentrations resulted in a decrease in activity arising from solvation of the hydrophobic sulfide, disrupting binding to the catalyst. In alcohols 10 the yield of product was decreased arising from increased rates of MP-11 deactivation via the formation of aldehydes (for primary alcohols) or by peroxide deactivation. The catalytic activity of cyclodextrin modified MP-11 was similar to that of MP-11 itself, demonstrating that it is the Ntermianal side of MP-11 which is the determinant of catalytic activity. Introduction 15The function of enzymes and proteins in non-aqueous solvents has been well established and, in some cases, commercialised [1][2][3][4][5] . Enzyme catalysis and biosensing in organic solvents offers many advantages over aqueous-based processes including increased substrate/analyte solubility, enhanced thermal stability, more 20 favourable reaction thermodynamics, ease of product / biocatalyst recovery and modified selectivity 1,2,[6][7][8][9][10] . The peroxidases are an important group of enzymes which catalyse a wide variety of synthetically useful oxidation reactions using peroxides as oxidants. In spite of this, their potential in non-aqueous catalytic 25 systems has yet to be realised. This may, in part, be attributed to deactivation of the enzymes by the peroxide oxidant at the concentrations required for such reactions [10][11][12] . Strategies to overcome this problem have been developed, including the slow addition 13 or in-situ generation 14 of the peroxide. Alternatively, 30 studies have shown that a high concentration of substrate relative to the peroxide aids the regeneration of the native enzyme and prevents the formation of the peroxidase intermediates which result in enzyme deactivation [15][16][17] . Microperoxidases (MPs) are the products of the proteolytic 35 digestion of cytochrome c. MP-11 contains residues 11 -21 of the parent protein and is prepared by the action of pepsin on cytochrome c. The haem group is covalently attached to the Cys14 and Cys17 residues via sulfide bonds and is coordinated on the proximal side by the imidazole nitrogen of His18. The 6th axial 40 ligand position is either unoccupied or loosely coordinated by water 18 . In this respect the haem configuration is analogous to that of the peroxidase enzymes and MP-11 displays typical peroxidase activity.The array of reactions catalysed by MPs is extensive. The 45 oxidation of phenolic substrates 17,19,20 , peroxide decomposition 21 , sulfide oxidation 22 , Mn 2+ oxidation 23 , the nitration of phenol in the presence of NO 2 -24 , the oxidation of N-methylcarbazole 25 and the dehalogenation of halophenols 26 have all been reported. Thus MPs display activity similar not on...

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Section: Kinetics Of Sulphide Oxidationsupporting

confidence: 73%

The effect of solvent on the catalytic properties of microperoxidase-11

O’Reilly

Magner

2011

Phys. Chem. Chem. Phys.

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“…In addition, at a higher pH (6.08) an apparent Q band at ca. 530 nm and a shoulder on the right side due to low-spin heme complex were displayed (see the red, blue and green curves), which is a signature of the formation of polymeric MP-11 [13,14,16,18,33,34].…”

Section: Mp-11 Immobilizationmentioning

confidence: 96%

“…MP-11 molecules easily form aggregates in solutions even at a submicromolar concentration, and at neutral and basic pH [13][14][15][16]. In order to compare directly the spectroscopic behaviour of MP-11 loaded into SMCs, we firstly investigated the solution spectra of MP-11 as a function of pH.…”

Section: Mp-11 Immobilizationmentioning

confidence: 99%

“…At pH 4.00, MP-11 is positively charged and water serves as the sixth ligand of Fe(III) atom. In this case, the monomer is its main form in the solution [13,18], which displays a characteristic spectrum of a ferric heme group with a strong Soret band at 396 nm, a poorly resolved Q band in the 500 $ 600 nm range and a shoulder due to ligand-to-metal transfer at about 620 nm (see the black curve). Upon increasing the solution pH to 4.85 and 5.39, the spectrum exhibits a split Soret band with a shoulder at the longer wavelength side and an increase in intensity of the Q band (see the red and blue curves).…”

Section: Mp-11 Immobilizationmentioning

confidence: 99%

“…Unfortunately, MP-11 suffers severe aggregation in solutions even at a submicromolar concentration, and at neutral and basic pH [13][14][15][16]. The aggregation results in a less accessibility for the heme group and a mixed spin-state of iron atom, thereby affecting its actual electrochemical activity and complicating the interpretation of its structurally dependent properties.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Adsorption of Microperoxidase-11 in Vertical Silica Mesochannels and Electrochemical Investigation of Its Electron Transfer Properties

Wang

Yang

2015

Electrochimica Acta

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pH‐induced reorientation of microperoxidase‐11 in mesoporous molecular sieves

Zhang

Donohoe

Bailey

2006

J Raman Spectroscopy

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The resonance Raman spectra of microperoxidase-11 loaded into the siliceous materials MCM-41 and SBA-15 demonstrate a pH dependence indicative of a protonation event on the substrate. An unusual change in relative Raman intensities without a shift in wavenumbers is observed upon lowering the system pH. Protonation of the silica surface is suggested to induce a reorientation of the MP-11 fragments within the silica framework.

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Hemepeptide models for hemoproteins: the behavior of -acetylmicroperoxidase-11 in aqueous solution

Cited by 48 publications

References 32 publications

The effect of solvent on the catalytic properties of microperoxidase-11

The effect of solvent on the catalytic properties of microperoxidase-11

Adsorption of Microperoxidase-11 in Vertical Silica Mesochannels and Electrochemical Investigation of Its Electron Transfer Properties

pH‐induced reorientation of microperoxidase‐11 in mesoporous molecular sieves

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