Kinetic study of the oxidation mechanism of glutathione by hydrogen peroxide in neutral aqueous medium

Abstract

The oxidation kinetics of glutathione (GSH) by hydrogen peroxide has been studied at neutral pH for different concentration ratios [GSH]0/[H2O2]0 between 0.2 and 2 (5 × 10−4 M ≤ [H2O2]0 ≤ 2.5 × 10−3M; 4 × 10−4 M ≤ [GSH]0 ≤ 2.5 × 10−3 M). In all cases studied, glutathione disulfide GSSG is the main product formed via two different oxidation ways, each of them contributing respectively to 80–85% and 10–15%.Our kinetic data indicate that an important fraction of hydrogen peroxide disappears without oxidizing the thiol function. This can be attributed to a combination between GSH and H2O2 protecting the sulfide group. Chemical evidences of the existence of a peroxide bond with GSSG are described. In our experimental conditions, the overall oxidation equation is 2mol GSH reacting with 2mol H2O2 giving 1mol GSSG. It is very different from the usually accepted stoichiometric reaction:[Formula: see text]A kinetic scheme is proposed and the corresponding rate constants are determined. Keywords: glutathione, hydrogen peroxide, kinetic mechanism, glutathione disulfide.

Vibrational spectroscopic study of glutathione complexation in aqueous solutions

“…According to our previous work, 7 the following scheme has been proposed to describe the action of hydrogen peroxide on glutathione in aqueous medium buffered at pH 7: The evolution of the inverse of the S-H intensity versus time gives a straight line that confirms that a second-order reaction is a rate-limiting step. The S-H intensity is converted into concentration (Fig.…”

“…In our previous investigation, 7 concerning the mechanism of oxidation of glutathione by hydrogen peroxide at neutral pH in vitro and in absence of enzyme, the formation of a complex involving GSH and H 2 O 2 has been put in evidence. By op- tical density measurements, the thermodynamic equilibrium constant of the formation of this complex has been estimated to be 1950 Ϯ 50 mol Ϫ1 l. Glutathione disulfide GSSG was the main product formed at the end of the overall process.…”

Formation of Superoxochromium(III) by a Novel Mechanism

“…The effect of H 2 O 2 on the yield of CrOO 2+ (Figure 10) can be explained by the reaction of hydrogen peroxide with the thiol, since initial addition of H 2 O 2 to the reacting system led to suppression of CrOO 2+ formation in a stoichiometric ratio close to that of its reaction with the thiol (2HRSH + H 2 O 2 = HRSSRH + 2H 2 O) [53]. Finally, the decrease in the yield of CrOO 2+ by addition of Dribose or 2-deoxy-D-ribose ( Figure 10, inset) may be explained by the reductive scavenging of the intermediate chromium(IV) by these additives, thus decreasing the rate of recuperation of CrOO 2+ through Equation (16), since these RNA-and DNA-forming carbohydrates react with chromium(VI) at a significant rate only in acid media [54], although a very slow reaction of ribonucleotides (but not deoxyribonucleotides) with chromium(VI) yielding chromium(V) has been reported in neutral solutions [55].…”

On N-acetylcysteine. Part I. Experimental and theoretical approaches of the N-acetylcysteine/H2O2complexation

“…(6). It has also been shown that glutathione disulfide, GSSG, is As we know, GSH is an intracellular cysteine-containing tripepthe main product formed via two different routes of oxidation, tide (y-glutamylcysteinylglycine) which plays many essential one contributing 80-85% and the other 10-15% (2) of the overroles in vivo, particularly as a defence against electrophylic all Process.…”