Gorren A C, Schmidt K, Mayer B
Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, Graz, Austria.
Arch Biochem Biophys. 1996 Jun 15;330(2):219-28. doi: 10.1006/abbi.1996.0247.
The decomposition of S-nitrosoglutathione (GSNO) in the presence of Cu2+ and glutathione (GSH) was studied by stopped-flow/rapid-scan spectroscopy. Reduction of Cu2+ by GSH and subsequent formation of a GS-*Cu+ complex occurred within 200 ms, with the amount of complex formed depending on the GSH-to-Cu2+ ratio. The rate of GSNO decomposition at a fixed concentration of Cu2+ increased linearly with the concentration of GSH at low GSH-to-Cu2+ ratios (< or = 0.2), but sharply declined at higher ratios. The same pattern was observed for the rate of NO. release, measured with an NO.-sensitive electrode. GSNO decomposition and NO. release in the presence of GSH and/or Cu2+ were completely inhibited by the Cu+ chelator neocuproine, but unaffected by the Cu2+ chelator cuprizone. Ascorbate and cysteine, which will reduce Cu2+ but have little or no affinity for Cu+, also stimulated GSNO decomposition in the presence of Cu2+, but did not inhibit it at higher concentrations. It is concluded that the homolytic cleavage of GSNO is efficiently catalyzed by Cu+ and that the GS-*Cu+ complex is catalytically inactive. By determining the anaerobic GSNO decomposition rates in the presence of varying concentrations of Cu+ a value of 4 x 10(3)M(-1) x s(-1) was derived for the apparent Cu+-GSNO association rate constant.
采用停流/快速扫描光谱法研究了在铜离子（Cu2+）和谷胱甘肽（GSH）存在下S-亚硝基谷胱甘肽（GSNO）的分解情况。谷胱甘肽将Cu2+还原并随后形成GS-*Cu+络合物的过程在200毫秒内发生，形成的络合物量取决于GSH与Cu2+的比例。在低GSH与Cu2+比例（≤0.2）时，固定浓度Cu2+条件下GSNO的分解速率随GSH浓度呈线性增加，但在较高比例时急剧下降。用对一氧化氮（NO·）敏感的电极测量的NO释放速率也观察到相同模式。在GSH和/或Cu2+存在下的GSNO分解和NO释放被Cu+螯合剂新铜试剂完全抑制，但不受Cu2+螯合剂双环己酮草酰二腙影响。抗坏血酸和半胱氨酸可还原Cu2+但对Cu+亲和力很小或没有亲和力，在Cu2+存在时也刺激了GSNO分解，但在较高浓度时不抑制。得出结论，GSNO的均裂裂解由Cu+有效催化，且GS-*Cu+络合物无催化活性。通过测定不同浓度Cu+存在下的厌氧GSNO分解速率，得出表观Cu+-GSNO缔合速率常数的值为4×10³M⁻¹×s⁻¹。
