Gow A J, Buerk D G, Ischiropoulos H
Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
J Biol Chem. 1997 Jan 31;272(5):2841-5. doi: 10.1074/jbc.272.5.2841.
The objective of this study was to investigate the mechanism of S-nitrosothiol formation under physiological conditions. A mechanism is proposed by which nitric oxide (.NO) reacts directly with reduced thiol to produce a radical intermediate, R-S-N.-O-H. This intermediate reduces an electron acceptor to produce S-nitrosothiol. Under aerobic conditions O2 acts as the electron acceptor and is reduced to produce superoxide (O-2). The following experimental evidence is provided in support of this mechanism. Cysteine accelerates the consumption of .NO by 2.5-fold under physiological conditions. The consumption of O2 in the presence of .NO and cysteine is increased by 2.4-fold. The reaction orders of .NO and cysteine are second and first order, respectively. The second order of reaction for .NO may result from interaction between .NO and O-2 to form peroxynitrite. In the presence of Cu,Zn-superoxide dismutase, the reaction of .NO with cysteine generates hydrogen peroxide, indicating that the reaction generates O-2. Finally, the formation of S-nitrosothiol is demonstrated in an anaerobic environment and, as predicted by the mechanism, is dependent on the presence of an electron acceptor. These results demonstrate that under physiological conditions .NO reacts directly with thiols to form S-nitrosothiol in the presence of an electron acceptor.
本研究的目的是探究生理条件下S-亚硝基硫醇形成的机制。我们提出了一种机制，即一氧化氮（·NO）直接与还原型硫醇反应生成自由基中间体R-S-N·-O-H。该中间体还原电子受体以生成S-亚硝基硫醇。在有氧条件下，O2作为电子受体被还原生成超氧化物（O2-）。以下实验证据支持了这一机制。在生理条件下，半胱氨酸使·NO的消耗加速2.5倍。在存在·NO和半胱氨酸的情况下，O2的消耗增加2.4倍。·NO和半胱氨酸的反应级数分别为二级和一级。·NO的二级反应可能是由于·NO与O2-相互作用形成过氧亚硝酸盐所致。在存在铜锌超氧化物歧化酶的情况下，·NO与半胱氨酸的反应生成过氧化氢，表明该反应生成了O2-。最后，在厌氧环境中证明了S-亚硝基硫醇的形成，并且正如该机制所预测的，其形成依赖于电子受体的存在。这些结果表明，在生理条件下，·NO在电子受体存在的情况下直接与硫醇反应形成S-亚硝基硫醇。
