Abstract
Peptide-bound advanced glycation end-products (peptide-bound AGEs) can be formed when peptides are heated with reducing saccharides. Pyrraline is the one of most commonly studied AGEs in foods, but the relative importance of the precursor peptide structure is uncertain. In the present study, model systems were prepared by heating peptides with glucose from 60 °C to 220 °C for up to 65 min, and the amounts of peptide-bound pyrraline formed were monitored to evaluate the effect of the neighboring amino acids on the peptide-bound pyrraline formation. The physico-chemical properties were introduced to explore the quantitative structure-reactivity relationships between physicochemical properties and peptide bound formation. 3-DG content in dipeptide-glucose model system was higher than that in the corresponding tripeptide-glucose model systems. Dipeptides produced higher amounts of peptide-bound pyrraline than the corresponding tripeptides. The peptide-bound pyrraline and 3-DG production were influenced by the physico-chemical properties of the side chain of amino acids adjacent to Lys in the following order: Lys-Leu/glucose > Lys-Ile/glucose > Lys-Val/ glucose > Lys-Thr/glucose > Lys-Ser/glucose > Lys-Ala/ glucose > Lys-Gly/glucose; Lys-Leu-Gly/glucose > Lys-Ile-Gly/glucose > Lys-Val-Gly/glucose > Lys-Thr-Gly/glucose > Lys-Ser-Gly/glucose > Lys-Ala-Gly/glucose > Lys-Gly-Gly/glucose. For the side chain of amino acids adjacent to Lys in dipeptides, residue volume, polarizability, molecular volume and localized electrical effect were positively related to the yield of peptide bound pyrraline, while hydrophobicity and pKb were negatively related to the yield of peptide bound pyrraline. In terms of side chain of amino acid adjacent to Lys in tripeptides, a similar result was observed, except hydrophobicity was positively related to the yield of peptide bound pyrraline.
Highlights
Since 1980, advanced glycation end products (AGEs), stable amino acid derivatives of the lysine and arginine side chains of proteins and peptides, have attracted increasing attention due to their pathophysiological role in diabetes [1,2,3,4]
It can be assumed that in foods, peptide- and protein-bound pyrraline formation derived from peptides and proteins by the Maillard reaction are much more important than the free-form pyrraline derived from free amino acids
Several physico-chemical properties were employed to explore the mechanism(s) that lead to differences in peptide- bound pyrraline formation among different peptide-glucose model systems
Summary
Since 1980, advanced glycation end products (AGEs), stable amino acid derivatives of the lysine and arginine side chains of proteins and peptides, have attracted increasing attention due to their pathophysiological role in diabetes [1,2,3,4]. It can be assumed that in foods, peptide- and protein-bound pyrraline formation derived from peptides and proteins by the Maillard reaction are much more important than the free-form pyrraline derived from free amino acids. A limited number of studies have been conducted on the reactivity of peptides in the Maillard reaction The majority of these studies have focused on the free amino acid, glycine homopolymer in model systems representing either physiological [15,16,17] or food-related conditions [17]. Seven different dipeptides and their corresponding tripeptides with lysine at the N-terminus (Lys-X and Lys-X-Gly, X = Ala, Gly, Ser, Ile, Leu, Thr, Val) were reacted with glucose to determine the factors that impact the peptide-bound pyrraline formation (Pyr-X and Pyr-X-Gly, X = Ala, Gly, Ser, Ile, Leu, Thr, Val). Several physico-chemical properties (i.e., hydrophobicity, polarizability, residue volume, pKb , localized electrical effect, molecular volume) were employed to explore the mechanism(s) that lead to differences in peptide- bound pyrraline formation among different peptide-glucose model systems
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