Modified Microperoxidases Exhibit Different Reactivity Towards Phenolic Substrates

Dallacosta, Corrado; Casella, Luigi; Monzani, Enrico

doi:10.1002/cbic.200400175

Cited by 18 publications

(18 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…23% added methanol. This result is a strong indication that competitive solvation of the substrate is responsible for the observed decrease in sulfoxidation activity at higher alcohol 20 concentrations. If this were the case, then a more hydrophilic substrate which would bind more strongly to the peptide of MP-11 should also show improved activity at high solvent concentrations.…”

Section: Effect Of Alcohols On Mp-11 Activitymentioning

confidence: 66%

“…The resulting haem aggregates were removed by centrifugation, dissolved in HPLC mobile phase and analysed as described below. The peak for the haem aggregates eluted at the same time for both MP-11 and CD-NAcMP-11 (9.5 minutes), thus indicating that the site of substitution was on the Glu21 residue on 20 the peptide and not on the haem propionates.…”

Section: Equationmentioning

confidence: 90%

“…The oxidation of methyl phenyl sulfide by MP-11 was also 15 observed in aqueous-solvent mixtures. Figure 6 displays the results for a number of solvents with the values of  0 and the % sulfide conversion in selected solvent mixtures listed in Table 2 (based on the optimum level of solvent in the case of the alcohols or the maximum amount of added solvent at which a reaction was 20 observed for the other solvents). A number of trends in the data are apparent: (i) the initial oxidation rate is significantly lower at high solvent concentrations than in aqueous buffer (by one order of magnitude in the case of 90% methanol), (ii) alcohols promote the oxidation reaction up to a certain threshold concentration after 25 which a steady decrease in activity is observed.…”

Section: Kinetics Of Sulphide Oxidationmentioning

confidence: 99%

“…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 1,2,6-10 . The peroxidases are an important group of enzymes which catalyse a wide variety of synthetically useful oxidation reactions using peroxides as oxidants.…”

mentioning

confidence: 99%

“…A sulfoxide was chosen as they are increasingly being used as 20 starting materials for the asymmetric synthesis of biologically active compounds 39 . In addition, many organic sulfides are insoluble in water, thus necessitating the use of organic solvents during biocatalysis.…”

mentioning

confidence: 99%

See 4 more Smart Citations

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

O’Reilly

Magner

2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

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...

show abstract

Section: Effect Of Alcohols On Mp-11 Activitymentioning

confidence: 66%

Section: Equationmentioning

confidence: 90%

Section: Kinetics Of Sulphide Oxidationmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

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

O’Reilly

Magner

2011

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

Heme Binding Induces Dimerization and Nitration of Truncated β‐Amyloid Peptide Aβ16 Under Oxidative Stress

et al. 2013

Self Cite

View full text Add to dashboard Cite

Several observations suggest a link between (ferric) heme and Alzheimers disease (AD), for example, an increase in heme oxygenase 1, [1,2] a loss of complex IV, [3][4][5][6] and abnormal iron metabolism. These observations suggest that heme metabolism is altered in age-related disorders. As a possible explanation, hemin has been proposed to interact with b-amyloid peptides (Ab), [7] and it is now well established that Ab peptides bind ferric heme. [8] The adducts of hemin-Ab peptides also exhibit increased peroxidase activity with respect to free hemin, [9] but these complexes have not been characterized. Herein we provide thermodynamic and spectroscopic data showing that hemin b can coordinate two Ab16 molecules to form the low-spin, six-coordinated complex [hemin(Ab16) 2 ], and this is in equilibrium with the high-spin [hemin(Ab16)] species, the relative amounts of which strongly depend on peptide concentration and temperature. In the presence of H 2 O 2 , hemin-Ab16 complexes produce dimerization of the peptide through dityrosine cross-linking, and in addition the peptide undergoes endogenous nitration at Tyr10 when nitrite is also present in solution. This result is important because both cross-linking and nitration at Tyr10 critically enhance Ab aggregation and plaque formation, [10] thus showing that the binding of heme to Ab can indeed be a factor contributing to neuroinflammation and Ab aggregation. The endogenous peroxidative (H 2 O 2 ) and nitrative (H 2 O 2 /NO 2 À ) activities exhibited by the hemin-Ab16 peptide add to, and are likely more deleterious than, the oxidation [9] and nitration [11] of external substrates which have been previously reported.Upon adding Ab16 to a 50 mm aqueous phosphate buffer solution of hemin b at pH 7.4 and 300 K, the broad Soret band of the complex near l = 385 nm progressively changes to give a sharp, red-shifted band at l = 414 nm, with additional visible bands at l = 535 and 566 nm (Figure 1 C, and see the Supporting Information). The conversion from the high-spin to the low-spin hemin species is complete after addition of 20 equivalents of Ab16, and spectrophotometric data analysis (see the Supporting Information) confirms a 2:1 Ab16/hemin stoichiometry, thus indicating the formation of the [hemin-(Ab16) 2 ] complex. The Mçssbauer and 1 H NMR spectra are consistent with a low-spin (S = 1/2) iron(III) center coordinated by two axial imidazole ligands. However, below saturating amounts of Ab16, the Mçssbauer spectrum clearly indicates the presence of a minor high-spin species (Figure 2). Figure 1. UV/vis spectra recorded in 50 mm phosphate buffer solution at pH 7.4. A) Hemin b (1.2 10 À5 m). B) Hemin b in the presence of an excess (20 equiv) of Ab16 peptide at 319 K. C) The same as (B) but at 300 K, the spectral changes are fully reversible. The D symbol indicates an increase in temperature.Figure 2. Mçssbauer spectrum of hemin b (2 mm), in the presence of 6 equivalents of the Ab16 peptide, recorded at 78 K. Quadrupole doublet simulation reveals the presence of a major...

show abstract