Reactivity and mechanism of the reactions of 4-methylbenzoquinone with amino acid residues in β-lactoglobulin: A kinetic and product investigation
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- Reactivity and mechanism of the reactions of 4-methylbenzoquinone with amino acid residues in β-lactoglobulin
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Quinones, produced by the oxidation of phenolic compounds, covalently bind to nucleophilic groups on amino acids or proteins. In this study, the reactions of 4-methylbenzoquinone (4MBQ) with β-lactoglobulin (β-LG) and amino acids at neutral pH were investigated. LC-MS analysis revealed that Cys121 was likely the most modified residue in β-LG. Identification of reaction products by LC-MS/MS showed that Michael addition occurred in all reactions with amino acids tested. The formation of Schiff base and a di-adduct was found in His and Trp samples. Apparent second-order rate constants (k2) were determined at 25 °C and pH 7.0 by stopped-flow spectrophotometry. The rate of reactions decreased in the order: β-LG > His > Trp > Arg > Nα-acetyl His > Nα-acetyl Arg > Nα-acetyl Trp. The rate constants correlated with the pKa values of the amino acids, showing that the amount of unprotonated amine is the major factor determining the reactivity.
Original language | English |
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Article number | 137473 |
Journal | Food Chemistry |
Volume | 434 |
Number of pages | 10 |
ISSN | 0308-8146 |
DOIs | |
Publication status | Published - 2024 |
Bibliographical note
Publisher Copyright:
© 2023 The Author(s)
- 4-methylcatechol, Kinetics, Michael addition, Polyphenol-protein binding, Protein modification, β-lactoglobulin
Research areas
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