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. Author manuscript; available in PMC: 2015 Jun 18.
Published in final edited form as: Biol Chem. 2015 May;396(5):415–444. doi: 10.1515/hsz-2015-0102

Figure 1. Thiol-chemistry of ROS, RES and HOCl with redox-sensing regulators.

Figure 1

Reversible thiol-oxidation by ROS leads first to a Cys sulfenic acid intermediate (R-SOH) that is unstable and reacts further to form intramolecular and intermolecular disulfides or mixed disulfides with LMW thiols, such as glutathione, bacillithiol, cysteine or CoASH, termed as S-thiolations. The Cys sulfenic acid can be also overoxidized to Cys sulfinic and sulfonic acids. Reactive electrophiles (RES) such as quinones have been shown to act via the S-alkylation and oxidation mode with quinone-sensing redox regulators. HOCl causes first chlorination of Cys thiol goups to the unstable sulfenylchloride which react further to form protein disulfides and S-thiolations in the presence of proximal thiols. In the absence of another thiol the sulfenylchloride rapidly forms irreversible Cys sulfinic or sulfonic acids (Hawkins et al, 2003).