Characterization of bovine serum albumin glycated with glucose, galactose and lactose.

The non-enzymatic reaction between reducing sugars and proteins, known as glycation, has re- ceived increased attention from nutritional and medical research. In addition, there is a large interest in obtaining glycoconjugates of pure well-characterized oligosaccharides for biological research. In this study, glycation of bovine serum albumin (BSA) by d-glucose, d-galactose and d-lactose under dry-heat at 60°C for 30, 60, 120, 180 or 240 min was assessed and the glycated products studied in order to establish their biological recognition by lectins. BSA glycation was monitored using gel electrophoresis, determination of available amino groups and lectin bind- ing assays. The BSA molecular mass increase and glycation sites were investigated by mass spec- trometry and through digestion with trypsin and chymotrypsin. Depending on time and type of sugar, differences in BSA conjugation were achieved. Modified BSA revealed reduction of amino groups' availability and slower migration through SDS/PAGE. d-Galactose was more reactive than d-glucose or d-lactose, leading to the coupling of 10, 3 and 1 sugar residues, respectively, af- ter 120 minutes of reaction. BSA lysines (K) were the preferred modified amino acids; both K256 and K420 appeared the most available for conjugation. Only BSA-lactose showed biological rec- ognition by specific lectins.