A Spectrophotometric Study of Glutathione

Abstract

The ultraviolet and visible absorption spectra of glutathione in aqueous, alcohol, and alkaline solutions show four regions of selective absorption at 500, 325, 280 and 252mμ, associated with absorption of energy in the α–β carbon bond of the glutamic acid radical, the –SH group of the cysteyl radical, the peptide linkage, and the S–S bond of oxidized glutathione, respectively. The peptide band at 280mμ consists of two components whose location, definition, and intensity depend upon the solvent. This band is shifted toward the visible in alkaline and alcohol solutions, as is the ultraviolet continuum. The location of the latter indicates that the energy absorbed in the peptide dissociates glutathione into its constituent amino acids. Oxidation follows the absorption of energy of wave-length about 325mμ; the subsequent reduction of the oxidized molecules is affected by energy of wave-length 252mμ. These conclusions are supported by freezing-point measurements of the van’t Hoff dissociation factors of glutathione, glutamic acid, cysteine HCl, and glycine solutions before and after irradiation.