Recombinant and in vitro expression systems for hydrogenases: new frontiers in basic and applied studies for biological and synthetic H2 production.

This review focuses on recent progress in developing heterologous and recombinant expression as well as in vitro maturation systems for the biosynthesis of active [FeFe] and [NiFe]-hydrogenases, which catalyze the reversible reaction, H2 <--> 2e- + 2H+. Activities of [FeFe] and [NiFe]-hydrogenases produced from different recombinant and in vitro maturation approaches are compared. Examples of how hydrogenase expression supports basic and applied studies of these enzymes are presented, and barriers to achieving more viable biological and synthetic H2-production systems and catalysts are addressed.