NiFe NiFeSe enzymes

Marjory Stephenson and Leonard Stickland named the enzyme in 1931 (Stephenson and Stickland, 1931). There are five types of hydrogenase. Three of these are Ni proteins and one contains iron as the only transition metal. These proteins catalyze the reversible oxidation of dihydrogen gas (Eq. 7). A fifth class of hydrogenase lacks metals and catalyzes Eq. 8, but not Eq. 7. The Ni enzymes are classed into the NiFe, the NiFeSe, and the hydrogen sensors. All of these enzymes are bidirectional, although different enzymes exhibit a catalytic bias toward making or oxidizing H2. 

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