Enzyme-like activity of glycated cross-linked proteins in free radical generation.
Enzyme-like activity of glycated cross-linked proteins in free radical generation.
复制标题
糖化交联蛋白在自由基生成中的酶样活性。
DOI：
10.1111/j.1749-6632.2000.tb06185.x
复制
发表时间：
2000
影响因子：
5.2
通讯作者：
Chock,PB
中科院分区：
文献类型：
--
作者：
Yim,MB;Kang,SO;Chock,PB
摘要：研究了三碳α -二羰基甲基乙二醛糖基化反应生成的交联氨基酸和蛋白质的结构和性质。我们的结果表明，这些反应产生黄色荧光产物和几种自由基。从与丙氨酸的反应中，通过EPR光谱鉴定出三种类型的自由基：1)交联自由基阳离子，甲基乙二醛二乙酰亚胺阳离子自由基；2)甲基乙二醛自由基阴离子为反离子；3)超氧自由基阴离子只在有氧存在的情况下产生。甲基乙二醛对牛血清白蛋白的糖基化也产生了蛋白结合的、交联的自由基，可能是在丙氨酸中观察到的交联席夫碱的阳离子自由基。糖化蛋白在缺氧或添加金属离子的情况下将铁细胞色素还原为铁细胞色素。细胞色素的减少伴随着由蛋白质结合自由基产生的电子顺磁共振信号振幅的大幅增加。此外，糖基化蛋白在氧存在下催化抗坏血酸的氧化，而蛋白自由基信号消失。这些结果表明，蛋白质的糖基化产生了催化单电子氧化还原反应的活性中心。这个具有酶样特征的活性中心被认为是蛋白质的交联希夫碱/交联希夫碱自由基阳离子。它模拟了金属催化氧化体系的特性。这些结果共同表明，体内积累的糖化蛋白为催化自由基的形成提供了稳定的活性位点。
Abstract:The structure and property of cross‐linked amino acids and proteins produced by a three‐carbon α‐dicarbonyl methylglyoxal in glycation reaction were investigated. Our results showed that these reactions generated yellow fluorescent products and several free radical species. From the reaction with alanine, three types of free radicals were identified by EPR spectroscopy: 1) the cross‐linked radical cation, methylglyoxal diaklylimine cation radical; 2) the methylglyoxal radical anion as the counterion; 3) the superoxide radical anion produced only in the presence of oxygen. Glycation of bovine serum albumin by methylglyoxal also generated the protein‐bound, cross‐linked free radical, probably the cation radical of the cross‐linked Schiff base as observed with alanine. The glycated protein reduced ferricytochromecto ferrocytochromecin the absence of oxygen or added metal ions. This reduction of cytochromecwas accompanied by a large increase in the amplitude of the electron paramagnetic resonance signal originated from the protein‐bound free radical. In addition, the glycated protein catalyzed the oxidation of ascorbate in the presence of oxygen while the protein‐free radical signal disappeared. These results indicate that glycation of protein generates active centers for catalyzing one‐electron oxidation‐reduction reactions. This active center, which exhibits enzyme‐like character, was suggested to be the cross‐linked Schiff base/the cross‐linked Schiff base radical cation of the protein. It mimics the characteristics of metal‐catalyzed oxidation system. These results together indicate that glycated proteins accumulatedin vivoprovide stable active‐sites for catalyzing the formation of free radicals.