This is one of three E.coli hydrogenases synthesized in response to different physiological conditions. HYD1 is believed to have a role in hydrogen cycling during fermentative growth (By similarity). A + H2 = AH2 Binds 1 nickel ion per subunit. Heterodimer of a large and a small subunit. Belongs to the [NiFe]/[NiFeSe] hydrogenase large subunit family.