Borchardt R T, Smissman E E, Nerland D, Reid J R
J Med Chem. 1976 Jan;19(1):30-7. doi: 10.1021/jm00223a007.
6-Aminodopamine (6-NH2DA) and various analogs of 6-NH2DA have been evaluated for their ability to inactivate purified catechol O-methyltransferase (COMT) in vitro. The inactivation of COMT by these agents could be prevented by including an antioxidant in the preincubation mixture or by excluding oxygen; however, catalase did not protect the enzyme from inactivation. Substrate protection studies and kinetic studies suggested that the loss of enzyme activity resulted from the alkylation of an amino acid residue at the active site of COMT by the quinoid types products which were generated upon air oxidation of 6-NH2DA. In addition, we have explored in more detail the reactivity toward COMT of specific intermediates in the oxidation pathways of 6-NH2DA by using various 6-NH2DA analogs. From the above studies we have concluded that 6-aminodopamine-p-quinone (6-NH2DAQ) is perhaps the most toxic species toward COMT. However, the aminochromes which are formed from 6-NH2DAQ are also effective in inactivating COMT. The results of these studies have provided a useful model system for observing the interaction of 6-NH2DA and its oxidation products with proteins; in addition, it has provided additional insight into the topography of the active site of COMT.
已对6-氨基多巴胺（6-NH2DA）及其各种类似物在体外使纯化的儿茶酚-O-甲基转移酶（COMT）失活的能力进行了评估。在预孵育混合物中加入抗氧化剂或排除氧气可防止这些试剂使COMT失活；然而，过氧化氢酶并不能保护该酶免于失活。底物保护研究和动力学研究表明，酶活性的丧失是由于6-NH2DA在空气中氧化生成的醌型产物使COMT活性位点的一个氨基酸残基烷基化所致。此外，我们通过使用各种6-NH2DA类似物，更详细地探讨了6-NH2DA氧化途径中特定中间体对COMT的反应性。从上述研究中我们得出结论，6-氨基多巴胺-p-醌（6-NH2DAQ）可能是对COMT毒性最大的物质。然而，由6-NH2DAQ形成的氨基色素在使COMT失活方面也很有效。这些研究结果为观察6-NH2DA及其氧化产物与蛋白质的相互作用提供了一个有用的模型系统；此外，它还为深入了解COMT活性位点的拓扑结构提供了更多信息。
