Catalytic polarographic currents in the nickel-glutathione system. III. Catalytic hydrogen prewave

In a Ni2+-containing buffer solution at pH ∼7, glutathione (Glu) produces a catalytic hydrogen prewave with the half-wave potential -1.26 V vs. SCE. Glu is, however, much less active than cysteine, owing to the low stability of nickel complexes involving coordination via sulfhydryl and amide nitrogen. Addnl., Glu forms complexes without catalytic activity in which Ni2+ is attached to the terminal glutamyl residue. The equilibrium between active and inactive complexes results in some mechanistic features explained by the suggested reaction scheme.