Figure 7.

Inhibition of zinc transfer from MT-2 by GSH. MT (1.3 μM) was incubated with PAR (100 μM) in 0.2 M Tris⋅HCl, pH 7.4, in the presence of increasing amounts of GSH, and the reaction was followed by measuring the increase of absorbance at 500 nm of the zinc-PAR complex for 60 min. The number of zinc atoms released from MT was calculated on the basis of the formation of Zn(PAR)₂ (ɛ₅₀₀ = 61,500 M⁻¹⋅cm⁻¹). Inhibition is expressed as the decrease in the amount of zinc transferred. The dotted line is based on a simple model with one GSH binding site and a dissociation constant of 56 μM.