Chapter 3 - Hydrogenase

Abstract

Several evolutionary models proposed that molecular hydrogen (hydrogen) was the primary energy source on the early Earth, exerting a major influence on the origin of life. Hydrogenase, the enzyme catalyzing the interconversion of hydrogen into protons and electrons is thus considered as an ancestral invention, for which the molecular structure and architecture have been thoroughly adapted for specialized tasks, undertaken in peculiar environments, during the course of the evolution. Three different types of hydrogenase can be distinguished on the basis of the metal content of their active site, namely, NiFe-hydrogenase, FeFe-hydrogenase, and Fe-hydrogenase. Although they share common features, taxonomic distribution, maturation apparatus, and physiological role differ substantially between the three different classes of hydrogenases. These metalloenzymes are thus considered as a classical example of convergent evolution. The notion that “there is much to learn from nature” holds great promise for biohydrogen applications, and this has been demonstrated by the emergence of bioengineering strategies used to design synthetic metabolic pathways and improve the oxygen tolerance of hydrogenases. In this chapter, we provide an overview of the diversity and physiological role of hydrogenases.