Influence of Transketolase-Catalyzed Reactions on the Formation of Glycolaldehyde and Glyoxal Specific Posttranslational Modifications under Physiological Conditions.

In the present study, we investigated the role of transketolase (TK) in the modulation of glycolaldehyde driven Maillard reactions. In vitro experiments with recombinant human TK reduced glycolaldehyde and glyoxal induced carbonyl stress and thereby suppressed the formation of advanced glycation endproducts up to 70% due to the enzyme-catalyzed conversion of glycolaldehyde to erythrulose. This was further substantiated by the use of 13 C-labeled compounds. For the first time, glycolaldehyde and other sugars involved in the TK reaction were quantified in vivo and compared to nondiabetic uremic patients undergoing hemodialysis. Quantitation revealed amounts of glycolaldehyde up to 2 μM and highlighted its crucial role in the formation of AGEs in vivo. In this context, a LC-MS2 method for the comprehensive detection of sedoheptulose-7-phosphate, fructose-6-phosphate, ribose-5-phosphate, erythrose-4-phosphate, erythrulose, and glycolaldehyde in whole blood, plasma, and red blood cells was established and validated based on derivatization with 1-naphthylamine and sodium cyanoborohydride.