Akagawa Mitsugu, Sasaki Takeshi, Suyama Kyozo
Department of Applied Bioorganic Chemistry, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, Japan.
Eur J Biochem. 2002 Nov;269(22):5451-8. doi: 10.1046/j.1432-1033.2002.03243.x.
The levels of alpha-aminoadipic-delta-semialdehyde residue, the oxidative deamination product of lysine residue, in plasma protein from streptozotocin-induced diabetic rats were evaluated. alpha-Aminoadipic-delta-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 alpha-aminoadipic-delta-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 alpha-aminoadipic-delta-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.
对链脲佐菌素诱导的糖尿病大鼠血浆蛋白中赖氨酸残基的氧化脱氨产物α-氨基己二酸-δ-半醛残基水平进行了评估。在苯酚存在下，通过酸水解将α-氨基己二酸-δ-半醛转化为双酚衍生物，并通过高效液相色谱法进行测定。血浆蛋白分析显示，糖尿病患者的α-氨基己二酸-δ-半醛水平比正常对照组高两倍。此外，我们探究了通过美拉德反应进行的氧化脱氨作用，并证明在生理pH值和温度下，牛血清白蛋白的赖氨酸残基在与各种碳水化合物一起孵育且存在Cu2+的情况下会发生氧化脱氨。该实验表明，3-脱氧葡萄糖酮和甲基乙二醛是赖氨酸残基最有效的氧化剂。当反应从葡萄糖开始时，在存在Cu2+的情况下也会形成大量的α-氨基己二酸-δ-半醛。脱氧、过氧化氢酶和羟基自由基清除剂可显著抑制该反应。我们提出的氧化脱氨机制是斯特雷克型反应和活性氧介导的氧化作用。基于这些发现，我们提出了糖尿病中蛋白质氧化修饰的一种新机制，即通过美拉德反应使赖氨酸残基发生氧化脱氨。
