Glycosylation of lysine-containing pentapeptides by glucuronic acid: new insights into the Maillard reaction.
The formation of glycosylation products in model systems consisting of d-glucuronic acid (GlcA) and lysine-containing peptides, such as Lys-Gly-Gly-Phe-Leu (1), Gly-Lys-Gly-Phe-Leu (4) and Ac-Gly-Lys-Gly-Phe-Leu (6), was examined to evaluate the site specificity as well as the extent and nature of the modification. Peptides were reacted with GlcA either in solution or under dry-heating conditions. From the incubations performed in solution (MeOH), the corresponding (1-deoxy-D-fructofuranos-1-yluronic acid)-peptide derivatives (Amadori compounds) were isolated. Whereas reaction of 1 resulted in the formation of mono-glycosylated Amadori compound 2 with the sugar moiety attached to the N(epsilon)-amino group of the Lys residue and its di-glycosylated analogue 3, exposure of 4 to GlcA afforded only di-glycosylated peptide 5. From the incubation of GlcA with Ac-Gly-Lys-Gly-Phe-Leu (6) performed under mild dry-heating conditions (50 degrees C) in an environment of 75% relative humidity, besides Amadori compound 7, two new Maillard reaction products were isolated that contained 3-hydroxypyridinium (8) and 3-hydroxy-picolinic acid moiety (9). The mechanism for the formation of pyridinium products is discussed.
Horvat
Stefica
S
Division of Organic Chemistry and Biochemistry, Ruder Bosković Institute, POB 180, Zagreb, HR-10002, Croatia. shorvat@irb.hr
Roscić
Maja
M
D000595:Amino Acid Sequence; D020723:Glucuronic Acid / Q000737:chemistry*; D006031:Glycosylation; D008239:Lysine / Q000737:chemistry*; D015416:Maillard Reaction; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000737:chemistry
D009842:Oligopeptides; D011726:Pyridinium Compounds; D020723:Glucuronic Acid; D008239:Lysine