Samuni A, Krishna C M, Riesz P, Finkelstein E, Russo A
Division of Cancer Treatment, National Cancer Institute, Bethesda, Maryland 20892.
J Biol Chem. 1988 Dec 5;263(34):17921-4.
2-Ethyl-1-hydroxy-2,5,5-trimethyl-3-oxazolidine (OXANOH), the one-electron reduction product of the stable nitroxide radical, 2-ethyl-2,5,5-trimethyl-3-oxazolidinoxyl (OXANO), is reportedly oxidized by superoxide, and its oxidation has been proposed as a method for assaying superoxide. We find that superoxide can both reduce OXANO and oxidize OXANOH. The respective rate constants, k1 and k2, were determined using two superoxide-generating systems (xanthine oxidase/xanthine as well as ionizing radiation). OXANOH oxidation and OXANO reduction are both inhibitable by superoxide dismutase, pH-dependent (4.5-9.3), and result in a steady state distribution of [OXANO] and [OXANOH], independent of their initial concentrations, i.e. the OXANO/OXANOH couple exhibits a metal-independent superoxide dismutase-like function. Thus it provides a prototype for future development of improved low molecular weight superoxide dismutase mimics which will also function in cellular hydrophobic (aprotic) compartments such as membranes.
2-乙基-1-羟基-2,5,5-三甲基-3-恶唑烷（OXANOH）是稳定氮氧自由基2-乙基-2,5,5-三甲基-3-恶唑烷氧基（OXANO）的单电子还原产物，据报道它会被超氧化物氧化，并且其氧化反应已被提议作为一种测定超氧化物的方法。我们发现超氧化物既能还原OXANO，又能氧化OXANOH。使用两种超氧化物生成系统（黄嘌呤氧化酶/黄嘌呤以及电离辐射）测定了各自的速率常数k1和k2。OXANOH的氧化和OXANO的还原均受超氧化物歧化酶抑制，依赖于pH（4.5 - 9.3），并导致[OXANO]和[OXANOH]的稳态分布，与它们的初始浓度无关，即OXANO/OXANOH偶联物表现出与金属无关的超氧化物歧化酶样功能。因此，它为未来开发改进的低分子量超氧化物歧化酶模拟物提供了一个原型，这些模拟物也将在细胞疏水（非质子）区室如膜中发挥作用。
