Amadori product and age formation during nonenzymatic glycosylation of bovine serum albumin in vitro

Glucose reacts with the amino groups of protein to form a Schiff base that rearranges to form a ketoamine adduct. These early products eventually undergo irreversible chemical modifications generating advanced glycation end products (AGES). We reacted various sugars and sugar phosphates with bovine serum albumin allowing the formation of Amadori and AGE products. The rates of browning, Amadori and AGE products formed during incubations at 37 and 55°C were compared. The correlation between AGE fluorescence and bitopical (crosslinking) modifications in the protein have been evaluated. Pentoses generated maximum Amadori products. Sugar phosphates were found to be more potent in generating AGEs than free sugars as measured by fluorescence. Though glucose, fructose and glucose-6-P do not generate fluorescence comparable to pentoses, they generate high molecular weight aggregates. In contrast, ribose-5-P, which shows significantly higher AGE and pentosidine fluorescence than the other sugars, did not generate high molecular weight aggregates. We suggest that there may not be a direct correlation between the levels of Amadori products, AGEs and crosslinking.