First Steps in the Oxidation of Sulfur-Containing Amino Acids by Hypohalogenation: Very Fast Generation of Intermediate Sulfenyl Halides and Halosulfonium Cations

Mechanism Involving Hydrogen Sulfite Ions, Chlorite Ions, and Hypochlorous Acid as Key Intermediates of the Autocatalytic Chlorine Dioxide–Thiourea Dioxide Reaction

“…This straightforwardly suggests that hypochlorous acid is indeed a key intermediate because methionine is a very efficient HOCl scavenger. [28,33,34] Moreover, the addition of a small amount of chlorite ions into the reaction solution has a huge impact on the absorbance measured at the first time point. The chlorine dioxide concentration drops immediately within the mixing period of the reactants (see Figure 4).…”

Catalase-Peroxidase from Synechocystis Is Capable of Chlorination and Bromination Reactions

“…1E and 1F). Sulfur compounds are very effective in scavenging reactive halogen intermediates (21). When assayed according to Ellman (22) it was shown that GSH was oxidized completely in the KatG/H 2 O 2 /bromide or KatG/H 2 O 2 /chloride systems, whereas in the absence of halides glutathione oxidation in the system KatG/H 2 O 2 was very slow (not shown).…”

“…Formation of oxidized halogen molecules was also measured by following the absorbance increase at 353 nm using ⑀ (mM Ϫ1 cm Ϫ1 ) ϭ 25.5 for triiodide, and at 266 nm using ⑀ (mM Ϫ1 cm Ϫ1 ) ϭ 36.4 for tribromide (21). The equilibrium for the corresponding reactions are represented by reaction (6).…”

“…Oxidation of GSH by halogenating species can lead to disulfide (GSSG) formation following reactions (7) and (8) or to the formation of sulfenyl halides and sulfonic acids (21).…”

Chemical Modification of Proteins by Reactive Oxygen Species

“…Hypochlorous acid is a highly reactive compound that undergoes reactions with sulfur-containing amino acid residues (Folkes et al, 1995;Peskin and Winterbourn, 2001;Armesto et al, 2000). Reaction with cysteine residues leads to formation of-SCl derivatives, which may react with other cysteine residues to form disulfides or undergo further reactions to form sulfenic, sulfinic, and sulfonic acid derivatives.…”