One- and two-electron oxidation of thiols: mechanisms, kinetics and biological fates

ABSTRACT

The oxidation of biothiols participates not only in the defense against oxidative damage but also in enzymatic catalytic mechanisms and signal transduction processes. Thiols are versatile reductants that react with oxidizing species by one- and two-electron mechanisms, leading to thiyl radicals and sulfenic acids, respectively. These intermediates, depending on the conditions, participate in further reactions that converge on different stable products. Through this review, we will describe the biologically relevant species that are able to perform these oxidations and we will analyze the mechanisms and kinetics of the one- and two-electron reactions. The processes undergone by typical low-molecular-weight thiols as well as the particularities of specific thiol proteins will be described, including the molecular determinants proposed to account for the extraordinary reactivities of peroxidatic thiols. Finally, the main fates of the thiyl radical and sulfenic acid intermediates will be summarized.

Keywords:

• Cysteine
• peroxidases sulfenic acid
• thiol
• thiyl radical

Acknowledgements

This study was funded by grants from Universidad de la República (CSIC Grupos 767 and 46725), National Institutes of Health (1R01AI095173) to RR and L'Oréal–UNESCO, Uruguay to B.A.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Notes

¹IUPAC recommended names for peroxynitrite anion (ONOO^-) and its conjugated acid, peroxynitrous acid (ONOOH), are oxoperoxonitrate (1-) and hydrogen oxoperoxonitrate, respectively. The term peroxynitrite is used to refer to the sum of ONOO⁻ and ONOOH.