Peroxynitrite preferentially oxidizes the dithiol redox motifs of protein-disulfide isomerase

Abstract

Protein-disulfide isomerase (PDI) is a ubiquitous dithioldisulfide oxidoreductase that performs an array of cellular functions, such as cellular signaling and responses to cell-damaging events. PDI can become dysfunctional by post-translational modifications, including those promoted by biological oxidants, and its dysfunction has been associated with several diseases in which oxidative stress plays a role. Because the kinetics and products of the reaction of these oxidants with PDI remain incompletely characterized, we investigated the reaction of PDI with the biological oxidant peroxynitrite. First, by determining the rate constant of the oxidation of PDI's redox-active Cys residues (Cys 53 and Cys 397 ) by hydrogen peroxide (k 17.3 1.3 M 1 s 1 at pH 7.4 and 25 C), we established that the measured decay of the intrinsic PDI fluorescence is appropriate for kinetic studies.