Metal Complexation by the Peptide-Bound Maillard Reaction Products N^ε-Fructoselysine and N^ε-Carboxymethyllysine

Abstract

Although the Maillard reaction between proteins and carbohydrates is of central importance for food processing and in vivo processes, only little is known about changes of the metal-binding properties induced by protein glycation. The purpose of this study was to examine the complex formation of the quantitatively important peptide-bound Maillard reaction products (MRPs) N(epsilon)-fructoselysine and N(epsilon)-carboxymethyllysine with the biologically relevant metal ions copper(II) and zinc(II). The MRPs were synthesized as the N(alpha)-hippuryllysine derivatives in order to block the coordination function of the alpha-amino group. Stability constant measurements were performed in aqueous solution using pH potentiometry. N(alpha)-Hippuryl-N(epsilon)-fructoselysine forms moderate Cu(II) complexes (Log(10) K(1) = 5.8; Log(10) K(2) = 4.0) but fails to form any complexes with Zn(II). N(alpha)-Hippuryl-N(epsilon)-carboxymethyllysine gives slightly stronger complexes with Cu(II) (Log(10) K(1) = 7.3; Log(10) K(2) = 6.3), but again no complexation with Zn(II) was observed. These results show that post-translational modification of proteins by carbohydrates leads to the formation of new coordination centers for metal ions within a protein chain. Further studies are necessary to clarify the consequences of this phenomenon in terms of protein quality and physiological processes.

Interaction of Zinc, Ascorbic Acid, and Folic Acid in Glycation with Albumin as Protein Model

“…The posttranslational modification of proteins by carbohydrates leads to the formation of new coordination centers for metal ions within a protein chain. But no complexation of Zn (II) with Maillard reaction products Nε fructolysine and Nε carboxymethyl lysine was observed [31]. Similar results of the absence of peak for zinc binding are observed through our FTIR data, except for a new peak at 2,036 cm −1 , indicating presence of hydrogen bond or ionized compound in presence of zinc.…”

Modification of collagen in vitro with respect to formation of Nɛ-carboxymethyllysine

“…Saxena et al [34] showed that the Cu(II), Ca(II), and Zn(II) binding ability of proteins is related to their carboxymethyllysine content. Studies on metal complexation by the peptide-bound CML show also that post-translational modification of proteins by carbohydrates leads to the formation of new coordination centers for metal ions within a protein chain [35]. The binding of the redox-active metals by proteins can be linked to oxidative stress.…”

The interaction of metal ions with Maillard reaction products in a lactose–glycine model system

“…Participation of metals in the Maillard reaction and their incorporation into intermediate products is closely related to the biological availability of mineral elements (Delgrado-Andrade, Seiquer, Nieto, & Navarro, 2004;Morales, Fernández-Fraguas, & Jiménez-Pérez, 2005;Sarria & Vaquero, 2001, 2006Seiquer, Valverde, Delgrado-Andrade, & Navarro, 2000;Whitelaw & Weaver, 1989) and the chemical damage caused to some essential amino acids (Leclere, Birlouez-Aragon, & Meli, 2002;Seifert, Krause, Gloe, & Henle, 2004). According to several authors, the amounts of soluble and dialyzable Zn and Fe in model solutions or thermally treated products decreased significantly due to the interaction of reducing sugars and amino acids.…”

“…This order differs somewhat from the Irving-Williams order of transition metals complex stability: Mn 2+ < Fe 2+ < Co 2+ < Ni 2+ < Cu 2+ > Zn 2+ (Irving & Williams, 1953), which might suggest the presence of more than one type of ligand. The antioxidant or pro-oxidant activity of melanoidins as chelating agents of metal ions was also described (Leclere et al, 2002;Pokorny, 1991;Seifert et al, 2004;Umetsu, Ikeda, & Nguyen, 1999;Wen et al, 2005). The metal chelating ability of Maillard reaction products, the stability of the complexes formed and the accumulation of chromophores in the reaction systems depend on the type of cations and amino compounds and on the reaction conditions.…”