Submitted on February 22, 2006
Revised on March 27, 2006
Accepted on March 31, 2006
Formation of N
-succinyl-lysine in vivo: a novel marker fordocosahexaenoic acid-derived protein modification
Yoshichika Kawai, Hiroyuki Fujii, Miki Okada, Yoshikazu Tsuchie, Koji Uchida, and Toshihiko Osawa
Graduate School of Nutrition and Biosciences, The University of Tokushima, Tokushima 770-8503
Corresponding Author: y-kawai{at}nutr.med.tokushima-u.ac.jp
Free radical-catalyzed peroxidation of docosahexaenoic acid (DHA, C22:6/
-3) generates various lipid peroxidation products that covalently modify biomolecules such as proteins. Under a free radical-generating system, DHA significantly modified lysine residues in bovine serum albumin. Upon incubation of oxidized DHA with an amino-compound pyridoxamine or a lysine-containing peptide, N-propanoyl and N-succinyl adducts were determined to be the major modification products. The hydroperoxide levels in the oxidized DHA closely reflected the formation of the Nepsilon-succinyl-lysine (SUL) upon reaction with the peptide, indicating that the hydroperoxides of DHA represent a potential pathway for the formation of SUL. To detect the DHA-derived protein modification in vivo, we developed a monoclonal antibody (mAb2B12) specific to SUL and found that the antibody specifically reacts with the SUL moiety. The formation of SUL was then immunochemically demonstrated in the liver of mice fed with DHA followed by intraperitoneal injection of carbon tetrachloride (CCl4), a hepatic lipid peroxidation model. Immunoreactive materials with mAb2B12 were observed in the DHA + CCl4 group, but were not significant in the control, DHA alone, and CCl4 alone groups. These data suggest that the formation of DHA-derived adducts such as SUL may be implicated in the oxidative damage observed in DHA-enriched tissues.
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