Hydrogenase specific C-terminal endopeptidases, also called Hydrogen Maturation Proteases (H2MP). These enzymes belong to the peptidase family M52. Maturation of [FeNi] hydrogenases includes formation of the nickel metallocenter, proteolytic processing and assembly with other subunits. Hydrogenase maturation endopeptidases are responsible for the proteolytic processing, liberating a short C-terminal peptide by cleaving after a His or an Arg residue, e.g., HycI (E. coli) is involved in processing of HypE, the large subunit of hydrogenase 3. This cleavage is nickel dependent. This CD also includes such hydrogenase-processing proteins as HydD, HupW, and HoxW, as well as, proteins of the F420-reducing hydrogenase of methanogens (e.g., FrcD). Also included, is the Pyrococcus furiosus FrxA protein, a bifunctional endopeptidase/ sulfhydrogenase found in NADP-reducing hyperthermophiles.The Pyrococcus FrxA is not related to those found in Helicobacter pylori.