A "Seleno Effect" Differentiates the Roles of Redox Active Cysteine Residues in Plasmodium falciparum Thioredoxin Reductase.

ABSTRACT: Here, we introduce the concept of the "seleno effect" in the study of oxidoreductases that catalyze thiol/disulfide exchange reactions. In these reactions, selenium can replace sulfur as a nucleophile, electrophile, or leaving group, and the resulting change in rate (the seleno effect) is defined as kS/ kSe. In solution, selenium accelerates the rate of thiol/disulfide exchange regardless of its chemical role (e.g., nucleophile or electrophile). Here we show that this is not the case for enzyme catalyzed reactions and that the magnitude of the seleno effect can differentiate the role of each sulfur atom of a disulfide bond between that of an electrophile or leaving group. We used selenium for sulfur substitution to study the thiol/disulfide exchange step that occurs between the N-terminal

SUBMITTER: O'Keefe JP 

PROVIDER: S-EPMC5866731 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature