What is "hydrogenase"

n. (context enzyme English) Any enzyme that catalyzes the formation of hydrogen, or the reversible oxidation of hydrogen.

A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H), as shown below:

Hydrogen uptake is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulfate, carbon dioxide, and fumarate. On the other hand, proton reduction is coupled to the oxidation of electron donors such as ferredoxin (FNR), and serves to dispose excess electrons in cells (essential in pyruvate fermentation). Both low-molecular weight compounds and proteins such as FNRs, cytochrome c, and cytochrome c can act as physiological electron donors or acceptors for hydrogenases.

In enzymology, a hydrogenase (acceptor) is an enzyme that catalyzes the chemical reaction

H + A $\rightleftharpoons$ AH

Thus, the two substrates of this enzyme are H and A, whereas its product is AH.

This enzyme belongs to the family of oxidoreductases, specifically those acting on hydrogen as donor with other acceptors. The systematic name of this enzyme class is hydrogen:acceptor oxidoreductase. Other names in common use include H2 producing hydrogenase[ambiguous], hydrogen-lyase[ambiguous], hydrogenlyase[ambiguous], uptake hydrogenase[ambiguous], and hydrogen:(acceptor) oxidoreductase.

Hydrogenase (NAD+, ferredoxin) (, bifurcating [FeFe] hydrogenase) is an enzyme with systematic name hydrogen:NAD, ferredoxin oxidoreductase. This enzyme catalyses the following chemical reaction

2 H + NAD + 2 oxidized ferredoxin $\rightleftharpoons$ 5 H + NADH + 2 reduced ferredoxin

The enzyme from Thermotoga maritima contains a [Fe-Fe] cluster (H-cluster) and iron-sulfur clusters. I