谷胱甘肽和Ebselen对胰岛素硝化的抑制及其相互作用机理的研究

生物体内NO和超氧阴离子快速反应生成的过氧亚硝酸根离子(ONOO^-，peroxynitrite)是一种强细胞毒性物质，它诱导蛋白质酪氨酸残基硝化是其损伤生物系统的重要途径之一。为了探讨谷胱甘肽和ebselen对胰岛素硝化的抑制及其相互作用机理，采用UV-Vis、HPLC和ESI-MS等方法，研究了ONOO^-对胰岛素的硝化作用、小分子抗氧化剂谷胱甘肽(GSH)和ebselen对ONOO^-硝化胰岛素的影响以及它们之间的相互作用。结果表明单独的GSH和ebselen对ONOO^--引发的胰岛素硝化均有明显的抑制，而作为谷胱甘肽过氧化物酶(GPx)的底物GSH 与GPx的模型化合物ebselen之间存在相互拮抗作用，经过对其产物分析，确定其机理是GSH和ebselen能够直接反应生成一种加合物，从而抑制了GSH和ebselen各自的抗硝化能力。

Studies on Inhibition of Glutathione and Ebselen on Nitration of Insulin and Their Reaction Mechanism

Peroxynitrite (ONOO^-) is a potent cytotoxic agent produced by rapid combination of NO and O₂^·-. The nitration of tyrosine residues is one of major pathways that peroxynitrite damages biological system. To investigate the inhibition of glutathione (GSH) and ebselen on the nitration of insulin and their reaction mechanism, the nitration of insulin by peroxynitrite, inhibition of GSH and ebselen to the nitration and their reaction were studied by UV-Vis, HPLC and ESI-MS. Present results showed that GSH or ebselen could inhibit the nitration of insulin by peroxynitrite significantly, but there was an antagonism between GSH, a substrate of glutathione peroxidase (GPx), and ebselen, a mimic of GPx. The antagonism mechanism is proposed from the characterization of reaction product, an adduct formed from ebselen and GSH, thus causing a decrease in the inhibition ability of GSH and ebselen to nitration of insulin.