Mechanism of Protein Modification by Glyoxal and Glycolaldehyde, Reactive Intermediates of the Maillard Reaction

doi:10.1074/jbc.270.17.10017

Mechanism of Protein Modification by Glyoxal and Glycolaldehyde, Reactive Intermediates of the Maillard Reaction (*)

From the (1) Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106

^§Recipient of a Fellowship of the Deutsche Forschungsgemeinschaft, Germany. To whom correspondence should be addressed:
Inst. of Pathology, Case Western Reserve University, 2085 Adelbert Rd., Cleveland, Ohio 44106
. Tel.: 216-368-6613; Fax: 216-844-1810.

Abstract

The role of glyoxal and glycolaldehyde in protein cross-linking and N-(carboxymethyl)lysine (CML) formation during Maillard reaction under physiological conditions was investigated. Incubation of bovine serum albumin with these reagents lead to rapid formation of C-2-imine cross-links and CML. Initial CML formation rate from glyoxal was not dependent on oxidation, suggesting an intramolecular Cannizzaro reaction. CML formation from glucose/lysine or Amadori product of both was strongly dependent on oxidation. Blocking of Amadori product by boric acid totally suppressed CML formation from Amadori product, but only by 37% in the glucose/lysine system. Trapping of glyoxal with aminoguanidine hardly suppressed CML formation from Amadori product, whereas it blocked 50% of CML production in the glucose/lysine system. While these results would support a significant role for glucose autoxidation in CML formation, the addition of lysine to a glucose/aminoguanidine incubation system catalyzed glyoxal-triazine formation 7-fold, thereby strongly suggesting that glucose autoxidation is not a factor for glyoxal-mediated CML formation. Based on these results, it can be estimated that approximately 50% of the CML forming in a glucose/lysine system originates from oxidation of Amadori product, and 40-50% originates from a pre-Amadori stage largely independent from glucose autoxidation. This step may be related to the so-called Namiki pathway of the Maillard reaction.

Footnotes

↵* This work was supported by grants from the National Eye Institute (EY 07099) and the National Institute on Aging (AG 05601). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

CML

N-(carboxymethyl)lysine

GC/MS

coupled gas chromatography-mass spectrometry

HPLC

high performance liquid chromatography

BSA

bovine serum albumin

N-(glucitolyl)lysine

reduced Amadori product of glucose and lysine

TLC

thin-layer chromatography; t-Boc, t-butoxycarbonyl.