Modification of peptide lysine during Maillard reaction of D-glucose and D-lactose

摘要

In model experiments of 4-aminobutyric acid and N-acetyl-L-lysine with [l-~(13)C]-D-gIucose and [l-l3C]-D-lactose cleavage reactions into N~(epsilon)-formyllysine and N~(epsilon)-carboxymethyllysine (CML) were elucidated. The alphalpha-dicarbonyl cleavage reactions of the pyrraline and furosine route involve amine-assisted transformations, which easily undergo retro aldol cleavage. Analogous reactions were investigated in peptides by heating a synthesized heptapeptide (N~(alpha)-Ac-Lys-Lys-beta-Ala-Lys-beta-Ala-Lys-Gly) with D-glucose, [l-~(13)C]-D-glucose and D-lactose, respectively. The modified peptides were separated by RP-HPLC and were analyzed by high resolution MALD1-TOF mass spectrometry. In both experiments, the first lysine residue contained the Amadori reaction product. The second lysine residue was transformed into the Amadori reaction product or into N~(epsilon)-carboxyniethyl3ysme and N~(epsilon)-formyllysine, respectively. By collision-induced decomposition (CID)-ESI-MS/MS sequencing of the modified peptides, the corresponding lysine residues were identified and characterized by ~1H-, ~(13)O, 2d-1H/~(13)C- and ~1H/~1-NMR. The volatile reaction products of the model reactions were investigated by capillary GC/MS. I am comparing the results and the distribution of the key compounds in both model systems different formation pathways can be described.