title: Competitive kinetics as a tool to determine rate constants for reduction of ferrylmyoglobin by food components.
abstract: 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 × 10(4)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 × 10(3)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.
authors.affiliation: Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg, Denmark. Electronic address: Jongberg@food.ku.dk.
authors.forename: Sisse
authors.initials: S
authors.lastname: Jongberg
authors.affiliation: Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg, Denmark; Department of Biomedical Sciences, Building 4.5, Panum Institute, University of Copenhagen, Blegdamsvej 3, Copenhagen 2200, Denmark. Electronic address: mnl@food.ku.dk.
authors.forename: Marianne N
authors.initials: MN
authors.lastname: Lund
authors.affiliation: Heart Research Institute, 7 Eliza Street, Newtown, NSW 2042, Australia; Faculty of Medicine, University of Sydney, Sydney, NSW 2006, Australia. Electronic address: David.Pattison@hri.org.au.
authors.forename: David I
authors.initials: DI
authors.lastname: Pattison
authors.affiliation: Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg, Denmark. Electronic address: ls@food.ku.dk.
authors.forename: Leif H
authors.initials: LH
authors.lastname: Skibsted
authors.affiliation: Department of Biomedical Sciences, Building 4.5, Panum Institute, University of Copenhagen, Blegdamsvej 3, Copenhagen 2200, Denmark; Heart Research Institute, 7 Eliza Street, Newtown, NSW 2042, Australia; Faculty of Medicine, University of Sydney, Sydney, NSW 2006, Australia. Electronic address: davies@sund.ku.dk.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Davies
mesh_terms: D002392:Catechin / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry; D005033:Ethylmaleimide / Q000494:pharmacology; D007700:Kinetics; D008460:Meat; D008786:Metmyoglobin / Q000737:chemistry*; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000494:pharmacology*; D013662:Tea
chemical_list: D010936:Plant Extracts; D013662:Tea; C028048:ferrylmyoglobin; D008786:Metmyoglobin; D002392:Catechin; D003545:Cysteine; D005033:Ethylmaleimide
keywords: ABTS; Competitive kinetics; Ferrylmyoglobin; Myofibrillar proteins; Phenols; Plant extracts