2] Thiol/disulfide exchange equilibria and disulfidebond stability

Abstract

Publisher Summary Disulfide-bond formation is a versatile oxidation used biologically in diverse processes, such as enzyme catalysis, protection against oxidative damage, stabilization of extracellular proteins, and regulation of biological activity. Because disulfide formation is a reversible process, disulfide-bond stability often plays an important role in the biological utility of disulfide bonds. In turn, the ability to form and break a specific disulfide bond under appropriate biological conditions depends on the nature of the oxidant or reductant, the disulfide stability, the kinetics of the forward and reverse reactions, and the nature and redox state of the environment in which the reaction occurs. The stability of disulfide bonds in small molecules and proteins spans an enormous range, a factor of approximately 1011, corresponding to a free-energy difference of about 15 kcal/mol or a redox potential difference of 0.33 V. This chapter outlines the importance of reversible thiol/disulfide exchange and discusses some practical considerations in measuring disulfide bond stability.