¹H NMR studies of the reactions of copper(I) and copper(II) with D- penicillamine and glutathione

Reactions of copper ions with D-penicillamine (PSH) have been monitored by ¹H NMR spectroscopy in the presence and absence of glutathione (GSH) under aerobic as well as anaerobic conditions. In D₂O solution at pD = 7.4, PSH coordinates to Cu⁺ to form PS^--Cu⁺ under argon atmosphere as revealed from the broadening of each signal. In the presence of dioxygen, the complex was converted to the well-characterized purple cluster species consisting of Cu⁺, Cu²⁺, and PS^2-. Addition of GSH into this solution quickly decomposed the cluster by the reduction of Cu²⁺ to Cu⁺. The cluster species was, however, reproduced after several hours because of the oxidation of Cu⁺ back to Cu²⁺. The solution containing both PSH and GSH formed three possible disulfides, PSSP, GSSG, and PSSG, under aerobic conditions. Addition of Cu⁺ to this solution again produced the purple cluster through several redox reactions. On the basis of these results, it was concluded that the co- existence of PSH and/or PSSP with Cu⁺ and/or Cu²⁺ leads to the formation of the stable cluster species regardless of the presence or absence of the other thiols such as GSH. This must be one of the reasons why PSH works in living cells as an effective drug for the Wilson disease.