Wetlaufer D B, Saxena V P, Ahmed A K, Schaffer S W, Pick P W, Oh K J, Peterson J D
Adv Exp Med Biol. 1977;86A:43-50. doi: 10.1007/978-1-4684-3282-4_3.
Disulfide-containing proteins offer unique advantages for mechanistic studies of the formation of native three-dimensional structure from unordered, reduced precursors. The main advantage is that covalent intermediates are formed; by characterizing these intermediates, one obtains substantial information about the reaction pathway. Thiol-disulfide interchange is a major component of most oxidative mechanisms carrying thiol to disulfide; thus, it required some attention in its own right. Afinsen's descriptions of a "shuffle-ase" enzyme led us to examine the rates of the uncatalyzed exchange under physiologically plausible conditions. Somewhat surprisingly, we found that the rates for formation of several native proteins in uncatalyzed systems containing GSSG and GSH are as great as with the "shuffle-ase" enzyme, suggesting that a substantial portion of biological thiol oxidations proceed by uncatalyzed exchange. While thiol-disulfide exchange of course results in no net change in the oxidation level of a system, catalytic linkage of thiol or disulfide to other redox systems provides a mechanism for achieving net changes.
含二硫键的蛋白质为研究从无序、还原的前体形成天然三维结构的机制提供了独特优势。主要优势在于会形成共价中间体；通过对这些中间体进行表征，人们可以获得有关反应途径的大量信息。硫醇 - 二硫键交换是大多数将硫醇氧化为二硫键的氧化机制的主要组成部分；因此，其本身就需要一些关注。安芬森对一种“洗牌酶”的描述促使我们在生理上合理的条件下研究未催化交换的速率。有点令人惊讶的是，我们发现在含有氧化型谷胱甘肽（GSSG）和还原型谷胱甘肽（GSH）的未催化体系中，几种天然蛋白质的形成速率与“洗牌酶”催化时一样快，这表明相当一部分生物硫醇氧化是通过未催化交换进行的。虽然硫醇 - 二硫键交换当然不会导致体系氧化水平的净变化，但硫醇或二硫键与其他氧化还原体系的催化连接提供了一种实现净变化的机制。
