This group of endopeptidases include HupW enzymes that are specific to the cyanobacterial hydrogenase and are involved in the C-terminal cleavage of the hydrogenase large subunit precursor protein. Cyanobacterial nickel-iron (NiFe)-hydrogenases are found exclusively in the N2-fixing strains and are encoded by hup (hydrogen uptake) genes. These uptake hydrogenases are heterodimers with a large (hupL) and small subunit (hupS) and catalyze the consumption of the H2 produced during N2 fixation. Sequence similarity shows that the putative metal-binding resides are well conserved in this group of hydrogen maturation proteases. This group also includes such proteins as the hydrogenase III from Aquifex aeolicus.