Ozone Oxidizes Glutathione to a Sulfonic Acid

• Published in: Chemical research in toxicology 2009-01, Vol.22 (1), p.35-40
• Main Authors: Enami, Shinichi, Hoffmann, M. R, Colussi, A. J
• Format: Article
• Language: English
• Subjects: Glutathione - chemistry; Oxidation-Reduction; Ozone - chemistry; Spectrometry, Mass, Electrospray Ionization; Sulfonic Acids - chemistry
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx800298j

Biosurfaces are universally covered with fluid microfilms containing reduced glutathione (GSH) and other antioxidants whose putative roles include the detoxification of ambient ozone (O3). It is generally believed that O3 accepts an electron from the thiolate GS2− function [pK a(GS−) = 8.8] of GSH to produce thiyl GS•− radicals en route to the disulfide GSSG. Here, we report novel electrospray mass spectrometry experiments showing that sulfonates (GSO3 −/GSO3 2−), not GSSG, are the exclusive final products on the surface of aqueous GSH microdroplets exposed to dilute O3(g) for ∼1 ms. The higher reactivity of the thiolate GS2− toward O3(g) over the thiol GS− is kinetically resolved in this time frame due to slow GS− acid dissociation. However, our experiments also show that O3 will be largely scavenged by the more reactive ascorbate coantioxidant in typical interfacial biofilms. The presence of GSSG and the absence of GSO3 −/GSO3 2− in extracellular lining fluids are therefore evidence of GSH oxidation by species other than O3.