RESUMO
Some properties of a hydrogenase from the recently isolated phototrophic sulfur bacterium Lamprobacter modestohalophilus strain Syvash and its resistance to a number of inactivating factors have been investigated. The enzyme consists of two subunits, 64 and 30 kD; pI = 4.5. The optimal pH was 8.5-9.5 for hydrogen uptake and 4.0 for H2 evolution. Hydrogenase preparations were resistant to the effects of O2, CO, and temperature, revealing high stability under storage. A considerable inactivation of the enzyme was observed at temperatures above 80 degrees C; the temperature optimum of methyl viologen reduction by H2 was 85 degrees C. Inhibitory effects of Ni2+, Cd2+, and Mg2+ on the hydrogenase activity were shown to be reversible and competitive with respect to methyl viologen in the hydrogen oxidation reaction.
Assuntos
Proteínas de Bactérias/química , Bactérias Gram-Positivas/enzimologia , Hidrogênio/química , Hidrogenase/química , Paraquat/química , Proteínas de Bactérias/isolamento & purificação , Monóxido de Carbono/química , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Hidrogenase/isolamento & purificação , Metais/química , Oxirredução , Oxigênio , Subunidades Proteicas/químicaRESUMO
The effects of some metal ions on the activity and activation of Thiocapsa roseopersicina hydrogenase have been studied. Inhibitory effects of Ni2+ and Cd2+ on the catalytic activity of the enzyme were reversible and competitive with respect to methyl viologen (MV) in the reaction of hydrogen oxidation. The affinity of these metal ions to the enzyme increased significantly with increasing pH, suggesting that their interactions are determined by electrostatic forces. Cu2+ and Hg2+ irreversibly inhibited the hydrogenase activity. 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.