The behaviors of glutathione and related amino acids in the TiO2 photocatalytic system.

Glutathione is a tripeptide capable of diminishing active oxygen species in living cells. The photocatalytic decomposition of glutathione and related amino acids in TiO(2) suspension was investigated with (1)H NMR spectroscopy. The results suggest that both glutathione in reduced and oxidative forms is adsorbed on the TiO(2) surface by carboxyl or amino groups but not by the thiol group of the side chain which plays a crucial role in the glutathione cycle, to be degraded. This means that the function of glutathione cycle should be deteriorated in living cells by the adsorption. However, the decomposition rates are considerably low as compared with those of the constituent amino acids (Glu, Cys, and Gly), possibly reflecting the self-defensive property against active oxygen species.