Effect of heavy metal ions on barley ribulose-1,5-bisphosphate carboxylase

Abstract

Heavy metal ions (Cu2+, Cd2+, Pb2+, and Zn2+) in concentrations of 10-4 mol l-1 inhibit barley ribulose-1,5-bisphosphate carboxylase (RuBPC) (EC 4.1.1.39). The enzyme is inhibited most strongly by Cd2+ and Cu2+ and only very little by Zn2+-ions. Cu2+ and Zn2+-ions in concentrations of the order of 10-6 mol l-1 stimulate the RuBPC activity. The reaction of metal ions with the protein molecule of the enzyme is time dependent. The activation of the enzyme by Cu2+ and Zn2+-ions is the highest after 10 min incubation. Cd2+-ions in concentrations of 10-6 mol l-1 lead to a time dependent irreversible inhibition of the enzyme.