Competitive kinetics as a tool to determine rate constants for reduction of ferrylmyoglobin by food components

TY - JOUR

T1 - Competitive kinetics as a tool to determine rate constants for reduction of ferrylmyoglobin by food components

AU - Jongberg, Sisse

AU - Lund, Marianne Nissen

AU - Pattison, David I.

AU - Skibsted, Leif Horsfelt

AU - Davies, Michael Jonathan

PY - 2016

Y1 - 2016

N2 - Competitive kinetics were applied as a tool to determine apparent rate constants for the reduction of hypervalent haem pigment ferrylmyoglobin (MbFe(IV)=O) by proteins and phenols in aqueous solution of pH 7.4 and I = 1.0 at 25 °C. Reduction of MbFe(IV)=O by a myofibrillar protein isolate (MPI) from pork resulted in kMPI = 2.2 ± 0.1 × 104 M-1 s-1. Blocking of the protein thiol groups on the MPI by N-ethylmaleimide (NEM) markedly reduced this rate constant to kMPI-NEM = 1.3 ± 0.4 × 103 M-1 s-1 consistent with a key role for the Cys residues on MPI as targets for haem protein-mediated oxidation. This approach allows determination of apparent rate constants for the oxidation of proteins by haem proteins of relevance to food oxidation and should be applicable to other systems. A similar approach has provided approximate apparent rate constants for the reduction of MbFe(IV)=O by catechin and green tea extracts, though possible confounding reactions need to be considered. These kinetic data suggest that small molar excesses of some plant extracts relative to the MPI thiol concentration should afford significant protection against MbFe(IV)=O-mediated oxidation.

AB - Competitive kinetics were applied as a tool to determine apparent rate constants for the reduction of hypervalent haem pigment ferrylmyoglobin (MbFe(IV)=O) by proteins and phenols in aqueous solution of pH 7.4 and I = 1.0 at 25 °C. Reduction of MbFe(IV)=O by a myofibrillar protein isolate (MPI) from pork resulted in kMPI = 2.2 ± 0.1 × 104 M-1 s-1. Blocking of the protein thiol groups on the MPI by N-ethylmaleimide (NEM) markedly reduced this rate constant to kMPI-NEM = 1.3 ± 0.4 × 103 M-1 s-1 consistent with a key role for the Cys residues on MPI as targets for haem protein-mediated oxidation. This approach allows determination of apparent rate constants for the oxidation of proteins by haem proteins of relevance to food oxidation and should be applicable to other systems. A similar approach has provided approximate apparent rate constants for the reduction of MbFe(IV)=O by catechin and green tea extracts, though possible confounding reactions need to be considered. These kinetic data suggest that small molar excesses of some plant extracts relative to the MPI thiol concentration should afford significant protection against MbFe(IV)=O-mediated oxidation.

KW - ABTS

KW - Competitive kinetics

KW - Ferrylmyoglobin

KW - Myofibrillar proteins

KW - Phenols

KW - Plant extracts

U2 - 10.1016/j.foodchem.2015.11.120

DO - 10.1016/j.foodchem.2015.11.120

M3 - Journal article

C2 - 26775941

AN - SCOPUS:84949035774

SN - 0308-8146

VL - 199

SP - 36

EP - 41

JO - Food Chemistry

JF - Food Chemistry

ER -