Haratake Mamoru, Fujimoto Katsuyoshi, Ono Masahiro, Nakayama Morio
Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Biochim Biophys Acta. 2005 May 25;1723(1-3):215-20. doi: 10.1016/j.bbagen.2005.02.002. Epub 2005 Feb 24.
Selenotrisulfide (e.g., glutathione selenotrisulfide (GSSeSG)) is an important intermediate in the metabolism of selenite. However, its reactivity with biological substances such as peptides and proteins in the subsequent metabolism is still far from clearly understood, because of its chemical instability under physiological conditions. Penicillamine (Pen) is capable of generating a chemically stable and isolatable selenotrisulfide, PenSSeSPen. To explore the metabolic fate of selenite in red blood cells (RBC), we investigated the reaction of selenotrisulfide with human hemoglobin (Hb) using PenSSeSPen as a model. PenSSeSPen rapidly reacted with Hb under physiological conditions. From the analysis of selenium binding using the Langmuir type binding equation, the apparent binding number of selenium per Hb tetramer almost corresponded to the number of reactive thiol groups of Hb. The thiol group blockade of Hb by iodoacetamide treatment completely inhibited the reaction of PenSSeSPen with Hb. In addition, MALDI-TOF mass spectrometric analysis of the selenium-bound Hb revealed that PenSSe moiety binds to the beta subunits of Hb. Overall, the reaction of PenSSeSPen with Hb appears to involve the thiol exchange between Pen and the cysteine residues on the beta subunit of Hb.
硒三硫化物（例如谷胱甘肽硒三硫化物（GSSeSG））是亚硒酸盐代谢中的重要中间体。然而，由于其在生理条件下的化学不稳定性，其在后续代谢中与肽和蛋白质等生物物质的反应仍远未被清楚地理解。青霉胺（Pen）能够生成一种化学稳定且可分离的硒三硫化物，即青霉胺硒三硫化物（PenSSeSPen）。为了探究亚硒酸盐在红细胞（RBC）中的代谢命运，我们以PenSSeSPen为模型研究了硒三硫化物与人类血红蛋白（Hb）的反应。PenSSeSPen在生理条件下与Hb迅速反应。通过使用朗缪尔型结合方程分析硒结合情况，每个Hb四聚体的硒表观结合数几乎与Hb的反应性巯基数量相对应。用碘乙酰胺处理对Hb的巯基进行封闭完全抑制了PenSSeSPen与Hb的反应。此外，对结合硒的Hb进行基质辅助激光解吸电离飞行时间质谱分析表明，PenSSe部分与Hb的β亚基结合。总体而言，PenSSeSPen与Hb的反应似乎涉及Pen与Hbβ亚基上半胱氨酸残基之间的巯基交换。
