Hydrogenases and oxygen

Hydrogenases represent a heterogeneous group of enzymes consisting of three evolutionary unrelated classes, i.e. [NiFe], [FeFe] and [Fe] hydrogenases. They allow the uni-cellular organisms in which they are expressed to use hydrogen as energy source or to reduce protons as a sink for excess reduction equivalents. Because of this capability there is growing interest in exploiting these enzymes in the field of sustainable energy generation. However, most hydrogenases which are appealing in this context are reversibly or irreversibly inhibited by dioxygen. Here, we summarize the current picture of oxygen-induced inhibition of the different classes of hydrogenases and discuss possible avenues that might lead to tailored oxygen-robust enzyme variants.