Characterization of the soluble hydrogenase from Desulfovibrio africanus

The soluble hydrogenase from Desulfovibrio africanus has been isolated and characterized. The enzyme consists of two subunits of 65 kDa and 27 kDa. Its absorption spectrum is typical of an iron-sulfur protein. The protein contains 12 iron atoms, 10 labile sulfur atoms and 0.9 nickel atom per molecule. D. africanus hydrogenase is rapidly activated under reducing conditions and exhibits a specific activity of 570 mumoles H2 evolved/min/mg. The EPR spectrum of the oxidized enzyme shows no Ni(III) signals. Upon reduction under hydrogen, the protein sample exhibits signals due to nickel with g values at 2.21, 2.17 and 2.01 correlating with the active state of the enzyme.