Formation of advanced glycation end products by glyceraldehyde and glyceraldehyde-3-phosphate with proteins

The initial nonenzymatic modification of proteins by a sugar is a process known as glycation. Glycation then proceeds to form advanced glycation endproducts (AGE) which have been hypothesized to play a major role in chemical aging of proteins and the pathological complications in diabetes. Because of their importance in different fields such as food chemistry and clinical chemistry, glycation and AGE formation have been extensively studied using model systems consisting of amino acids, peptides or proteins with different reducing sugars.Elevated glucose levels in diabetes increases glycation of proteins, however metabolites from the glucose pathway can also be involved in non-enzymatic reactions with proteins. In the last decade most studies were focused on glycation of proteins by glucose and to a lesser extent by fructose, which is formed from glucose, and is the preferred metabolic sugar in some tissues. Glyceraldehyde is a product of fructose metabolism. It is a very simple sugar, and unlike glucose and fructose, it does not form hemiacetal ring structures in solution. Glyceraldehyde is therefore a very reactive glycating agent.In the present study, AGE was formed in different systems consisting of either proteins or amino acids incubated with reducing sugars under physiological conditions. Presence of AGE was monitored by ultraviolet and fluorescence spectroscopy. Capillary Electrophoresis, High Performance Liquid Chromatography, and Gas Chromatography were used to separate the different species formed under physiological conditions.