Purification and Characterization of Membrane-bound Hydrogenase from Hydrogenobacter thermophilus Strain TK-6, an Obligately Autotrophic, Thermophilic, Hydrogen-oxidizing Bacterium

抄録

  A membrane-bound hydrogenase was purified to electrophoretic homogeneity from the cells of Hydrogenobacter thermophilus strain TK-6, an obligately autotrophic, thermophilic, hydrogen-oxidizing bacterium. Solubilization and purification were done aerobically in the presence of Triton X-100. Three chromatography steps were done for purification; Butyl-Sepharose, Mono-Q, and Superose 6, in this order. Purification was completed with 6.73% yield of total activity and with 21.4-fold increase of specific activity when compared with the values for the membrane fraction. The purified hydrogenase was shown to be a tetramer with α₂β₂ structure, with a molecular mass of 60,000 Da for the large subunit and 38,000 Da for the small subunit. The purified hydrogenase directly reduced methionaquinone with an apparent K_m of around 300 μM and with a turnover number around 2900 (min^-1). Metal analysis and EPR properties of the hydrogenase have shown that the enzyme is one of the [NiFe]-hydrogenases. Also, optimum pH and temperature for reaction, thermal stability, and electron acceptor specificity were reported. Finally, a model is presented for energy and central metabolism of H. thermophilus strain TK-6.