The Reactivity of the Sulfhydryl Group in Glutathione and Related Peptides

Abstract

The reactivity of the sulfhydryl group in different thiols varies enormously. The changes in the reactivity of —SH groups under the influence of certain denaturing agents, as observed in proteins, are not confined to these macromolecules, but the reactivity of the —SH group of some small-molecular thiols, such as glutathione, can also be altered by some of the agents known to cause protein denaturation. The chemical reagents that have been used to bring about protein denaturation are urea and guanidinium salts. The results with guanidinium salts show that even in 7 M urea the —SH groups of the inhibited thiols are still not fully reactive as a further large increase in the nitroprusside color of glutathione occurs in the presence of 3 M concentrations of these salts. At pH values at which the —SH group is not yet ionized, hydrogen bonds could also be formed with the participation of the hydrogen atom of the —SH group itself.