Suzuki K T, Karasawa A
National Institute for Environmental Studies, Ibaraki, Japan.
Arch Biochem Biophys. 1990 Apr;278(1):120-4. doi: 10.1016/0003-9861(90)90239-u.
An albumin-copper-cysteine complex that has been shown to be formed in serum when cupric ion is injected intravenously into rats was reconstituted in vitro with mercaptalbumin, cupric ion, and cysteine in the presence of calcium ions. Mercaptalbumin was separated from fresh rat serum on a GS-520P column and the protein was incubated with an equimolar amount of cupric ions, which resulted in the formation of an albumin-copper complex. However, the albumin-copper complex did not form the albumin-copper-cysteine complex in the presence of cysteine at any of the molar ratios of cysteine to mercaptalbumin examined. Albumin-copper-cysteine complex was formed only when a more than equimolar amount of calcium to mercaptalbumin was present in the incubation mixture. The stoichiometric relationship revealed for the formation of albumin-copper-cysteine complex is mercaptalbumin: copper:cysteine:calcium = 1:1:2:1. One molar equivalent of cysteine was incorporated into the complex through disulfide bonds and another molar equivalent of cysteine was present unchanged after the reaction, suggesting that the latter cysteine participated in maintaining a specific conformation of albumin during formation of the complex. The overall reaction was oxidative and oxygen enhanced the reaction.
当向大鼠静脉注射铜离子时，血清中会形成一种白蛋白 - 铜 - 半胱氨酸复合物。在钙离子存在的情况下，用巯基白蛋白、铜离子和半胱氨酸在体外重建了该复合物。巯基白蛋白在GS - 520P柱上从新鲜大鼠血清中分离出来，然后将该蛋白质与等摩尔量的铜离子孵育，从而形成白蛋白 - 铜复合物。然而，在所检测的半胱氨酸与巯基白蛋白的任何摩尔比下，白蛋白 - 铜复合物在半胱氨酸存在时都不会形成白蛋白 - 铜 - 半胱氨酸复合物。只有当孵育混合物中存在超过等摩尔量的钙与巯基白蛋白时，才会形成白蛋白 - 铜 - 半胱氨酸复合物。所揭示的白蛋白 - 铜 - 半胱氨酸复合物形成的化学计量关系为：巯基白蛋白:铜:半胱氨酸:钙 = 1:1:2:1。一摩尔当量的半胱氨酸通过二硫键掺入复合物中，另一摩尔当量的半胱氨酸在反应后保持不变，这表明后者的半胱氨酸在复合物形成过程中参与维持白蛋白的特定构象。整个反应是氧化反应，氧气会增强该反应。
