In enzymology, a cytochrome-c3 hydrogenase () is an enzyme that catalyzes the chemical reaction 2 H2 + ferricytochrome c3 4 H+ + ferrocytochrome c3 Thus, the two substrates of this enzyme are H2 and ferricytochrome c3, whereas its two products are H+ and ferrocytochrome c3. This enzyme belongs to the family of oxidoreductases, specifically those acting on hydrogen as donor with a cytochrome as acceptor. The systematic name of this enzyme class is hydrogen:ferricytochrome-c3 oxidoreductase. Other names in common use include H2:ferricytochrome c3 oxidoreductase, cytochrome c3 reductase, cytochrome hydrogenase, and hydrogenase [ambiguous]. It has 3 cofactors: iron, Nickel, and Iron-sulfur. Structural studies As of late 2007, 19 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , , , , , , , , , , , , and . References EC 1.12.2 Iron enzymes Nickel enzymes Iron-sulfur enzymes Enzymes of known structure