PARTIAL-PURIFICATION AND CHARACTERIZATION OF THE 1ST HYDROGENASE ISOLATED FROM A THERMOPHILIC SULFATE-REDUCING BACTERIUM

A soluble [NiFe] hydrogenase has been partially purified from the obligate thermophilic sulfatereducing bacterium Thermodesulfobacterium mobile. A 17% purification yield was obtained after four chromatographic steps and the hydrogenase presents a purity index (A398nm/A277nm) equal to 0.21. This protein appears to be 75% pure on SDS-gel electrophoresis showing two major bands of molecular mass around 55 and 15 kDa. This hydrogenase contains 0.6-0.7 nickel atom and 7-8 iron atoms per mole of enzyme and has a specific activity of 783 in the hydrogen uptake reaction, of 231 in the hydrogen production assay and of 84 in the deuterium-proton exchange reaction. The H2/HD ratio is lower than one in the D2-H+ exchange reaction. The enzyme is very sensitive to NO, relatively little inhibited by CO but unaffected by NO2-. The EPR spectrum of the native hydrogenase shows the presence of a [3Fe-4S] oxidized cluster and of a Ni(III) species. © 1992 Academic Press, Inc.