In vitro covalent modification of serum albumin by acrolein

Amino acid analyses of human serum albumin treated with acrolein under in vitro conditions showed disappearance of lysine and histidine residues with concomitant appearance of four new peaks upon amino acid analyses. The first three peaks emerged just prior to histidine, while the fourth emerged between ammonia and arginine. Model compound (polyhistidine) treated with acrolein and subjected to amino acid analyses provided three peaks which eluted at the same positions as the first three peaks found in the acrolein-treated albumin. This provided tentative identification of the first three peaks as possible histindine-acrolein adducts. Likewise, model compound polylysine treated under the same conditions yielded a peak which corresponded to the fourth peak observed in the acrolein-treated albumin. There is a direct proportional increase in the adducts formed with increasing concentrations of acrolein. The chemical caused substantial increase in the absorbance of albumin at 280 nm indicating unfolding of the protein. Covalent modifications of the lysine and histidine residues by acrolein do not have any effect on the binding of palmitic acid or bromcresol green to albumin.