TAILIEUCHUNG - Báo cáo Y học: Oxidative deamination of lysine residue in plasma protein of diabetic rats Novel mechanism via the Maillard reaction

The levels ofa-aminoadipic-d-semialdehyde residue, the oxidative deamination product of lysine residue, in plasma protein from streptozotocin-induced diabetic rats were was converted to a bisphenol derivative by acid hydrolysis in the presence of phenol, and determined by high performance liquid chro-matography. Analysis of plasma proteins revealed three timeshigherlevelsofa-aminoadipic-d-semialdehyde in dia-betic subjects comparedwithnormal controls. | Eur. J. Biochem. 269 5451-5458 2002 FEBS 2002 doi Oxidative deamination of lysine residue in plasma protein of diabetic rats Novel mechanism via the Maillard reaction Mitsugu Akagawa Takeshi Sasaki and Kyozo Suyama Department of Applied Bioorganic Chemistry Division of Life Science Graduate School of Agricultural Science Tohoku University Japan The levels of a-aminoadipic-ỗ-semialdehyde residue the oxidative deamination product of lysine residue in plasma protein from streptozotocin-induced diabetic rats were evaluated. a-Aminoadipic-ỗ-semialdehyde was converted to a bisphenol derivative by acid hydrolysis in the presence of phenol and determined by high performance liquid chromatography. Analysis of plasma proteins revealed three times higher levels of a-aminoadipic-ỗ-semialdehyde in diabetic subjects compared with normal controls. Furthermore we explored the oxidative deamination via the Maillard reaction and demonstrated that the lysine residue of bovine serum albumin is oxidatively deaminated during the incubation with various carbohydrates in the presence of Cu2 at a physiological pH and temperature. This experiment showed that 3-deoxyglucosone and methylglyoxal are the most efficient oxidants of the lysine residue. When the reaction was initiated from glucose a significant amount of a-aminoadipic-ỗ-semialdehyde was also formed in the presence of Cu2 . The reaction was significantly inhibited by deoxygenation catalase and a hydroxyl radical scavenger. The mechanism we propose for the oxidative deamination is the Strecker-type reaction and the reactive oxygen species-mediated oxidation. Based on these findings we propose a novel mechanism for the oxidative modification of proteins in diabetes namely the oxidative deamination of the lysine residue via the Maillard reaction. Keywords Maillard reaction glycation reactive oxygen species a-aminoadipic-ỗ-semialdehyde oxidative deamination. The Maillard reaction nonenzymatic glycation

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