Abstract
Laser flash photolysis and high-resolution mass spectrometry were used to investigate the mechanism of one-electron oxidation of two S-alkylglutathiones using 3-carboxybenzophenone (3CB) as a photosensitizer. This report indicates an unexpected reaction pathway of the α-aminoalkyl radical cation (αN+) derived from the oxidation of S-alkylglutathiones. Instead of a common hydrolysis reaction of αN+ reported earlier for methionine and other sulfur-containing aminoacids and peptides, an intramolecular ring-closure reaction was found for S-alkylglutathiones.
Highlights
S-alkylglutathiones, as thioethers derived from glutathione (Glu), are considered as biologically relevant peptides
The transients formed in the photosensitized oxidation of peptides containing thioether group are transients[29,31,32,34,35,36,37,38,39]
The postulated fate of the α-aminoalkyl radicals (αN)+ carbocation is presented in Scheme SI
Summary
S-alkylglutathiones, as thioethers derived from glutathione (Glu), are considered as biologically relevant peptides (naturally occurring oligopeptides). They occur in plants, animals, and humans [1]. S-methylglutathione (S-Me-Glu, Figure 1) was found in yeasts [2], brain tissues [2,3], and Escherichia coli [4]. The synthesis of S-Me-Glu involves chemotaxis methyltransferase, glutathione, and S-adenosyl-methionine [4]. S-Me-Glu was found to be a metabolic product when various methylated drugs and pesticides were present [1]. When methyl halides are metabolized by glutathione S-transferases, S-Me-Glu is a common product [5]
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