Formation of N-epsilon-(Hexanonyl)lysine in protein exposed to lipid hydroperoxide - A plausible marker for lipid hydroperoxide-derived protein modification

The objectives of this study were to estimate the structure of the lipid hy droperoxide-modified lysine residue and to prove the presence of the adduct s in vivo. The reaction of lipid hydroperoxide toward the lysine moiety was investigated employing N-benzoyl-glycyl-L-lysine (Bz-Gly-Lys) as a model c ompound of Lys residues in protein and 13-hydroperoxyoctadecadienoic acid ( 13-HPODE) as a model of the lipid hydroperoxides. One of the products, comp ound X, was isolated from the reaction mixture of 13-HPODE and Bz-Gly-Lys a nd was then identified as N-benzoyl-glycyl-N-epsilon-(hexanonyl)lysine. To prove the formation of N-epsilon-(hexanonyl)lysine, named HEL, in protein e xposed to the lipid hydroperoxide, the antibody to the synthetic hexanonyl protein was prepared and then characterized in detail. Using the anti-HEL a ntibody, the presence of HEL in the lipid hydroperoxide-modified proteins a nd oxidized LDL was confirmed. Furthermore, the positive staining by anti-H EL antibody was observed in human atherosclerotic lesions using an immunohi stochemical technique. The amide-type adduct may be a useful marker for the lipid hydroperoxide-derived modification of biomolecules.