Study on the interaction of metallothionein with glutathione using ferrocenyl-labeled glutathione as an electrochemical probe

The interaction between glutathione (GSH) and metallothionein (MT) plays a critical role in metal release from MT in life processes. In this paper, the interaction was measured directly by voltammetric method at the MT-modified electrode, due to the attachment of the redox-active ferrocene moiety to GSH. Particularly, the covalent attachment of ferrocene moiety to GSH does not significantly perturb the GSH structure and its binding behavior with MT. The GSH/MT stoichiometry and binding constant Ka were obtained by cyclic voltammetric method and the values are 1.78 ± 0.15 and 5.44 ± 0.43 ×10⁶ M^-1, respectively. In addition, zinc release from MT in the presence of glutathione or glutathione disulfide (GSSG) was also studied by means of differential pulse voltammetry. The difference in binding constant between Zn-MT and GSH-MT complexes explains the inhibition of GSH on the zinc release from MT.