Hydrogenase

A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H₂), as shown below:

Hydrogen uptake (1) is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulfate, carbon dioxide, and fumarate. On the other hand, proton reduction (2) 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 c₃, and cytochrome c₆ can act as physiological electron donors or acceptors for hydrogenases.

Structural classification

It has been estimated that 99% of all organisms utilize dihydrogen, H₂. Most of these species are microbes and their ability to use H₂ as a metabolite arises from the expression of H₂metalloenzymes known as hydrogenases. Hydrogenases are sub-classified into three different types based on the active site metal content: iron-iron hydrogenase, nickel-iron hydrogenase, and iron hydrogenase.

Hydrogenase (acceptor)

In enzymology, a hydrogenase (acceptor) (EC 1.12.99.6) is an enzyme that catalyzes the chemical reaction

Thus, the two substrates of this enzyme are H₂ and A, whereas its product is AH₂.

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.

References

Hydrogenase (NAD+, ferredoxin)

Hydrogenase (NAD+, ferredoxin) (EC 1.12.1.4, bifurcating [FeFe] hydrogenase) is an enzyme with system name hydrogen:NAD⁺, ferredoxin oxidoreductase. This enzyme catalyses the following chemical reaction

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

References

External links