Document Type

Article

Subject Area(s)

Chemistry

Abstract

Dicarbonyl compounds such as glyoxal and methylglyoxal are reactive dicarbonyl intermediates in the nonenzymatic browning and cross-linking of proteins during the Maillard reaction. We describe here the quantification of glyoxal and methylglyoxal-derived imidazolium cross-links in tissue proteins. The imidazolium salt cross-links, glyoxal-lysine dimer (GOLD) and methylglyoxal-lysine dimer (MOLD), were measured by liquid chromatography/mass spectrometry and were present in lens protein at concentrations of 0. 02-0.2 and 0.1-0.8 mmol/mol of lysine, respectively. The lens concentrations of GOLD and MOLD correlated significantly with one another and also increased with lens age. GOLD and MOLD were present at significantly higher concentrations than the fluorescent cross-links pentosidine and dityrosine, identifying them as major Maillard reaction cross-links in lens proteins. Like the N-carboxy-alkyllysines Nepsilon-(carboxymethyl)lysine and Nepsilon-(carboxyethyl)lysine, these cross-links were also detected at lower concentrations in human skin collagen and increased with age in collagen. The presence of GOLD and MOLD in tissue proteins implicates methylglyoxal and glyoxal, either free or protein-bound, as important precursors of protein cross-links formed during Maillard reactions in vivo during aging and in disease.

Included in

Chemistry Commons

Share

COinS