Influence of metal ions on hydrogenase from the purple sulfur bacterium Thiocapsa roseopersicina

The effects of some metal ions on the activity and activation of Thiocapsa roseopersicina hydrogenase have been studied. Inhibitory effects of Ni2+ an d Cd2+ on the catalytic activity of the enzyme were reversible and competit ive with respect to methyl viologen (MV) in the reaction of hydrogen oxidat ion. The affinity of these metal ions to the enzyme increased significantly with increasing pH, suggesting that their interactions are determined by e lectrostatic forces. Cu2+ and Hg2+ irreversibly inhibited the hydrogenase a ctivity. A decrease in absorption of hydrogenase at 400 nm in the presence of these metal ions is indicative of the destruction of the FeS cluster in the enzyme.