Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:1.12.7.2 (
hydrogenase
)
3,522
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The Wood-Ljungdahl pathway of anaerobic CO(2) fixation with hydrogen as reductant is considered a candidate for the first life-sustaining pathway on earth because it combines carbon dioxide fixation with the synthesis of ATP via a chemiosmotic mechanism. The acetogenic bacterium Acetobacterium woodii uses an ancient version of the pathway that has only one site to generate the electrochemical ion potential used to drive ATP synthesis, the ferredoxin-fueled, sodium-motive Rnf complex. However, hydrogen-based ferredoxin reduction is endergonic, and how the steep energy barrier is overcome has been an
enigma
for a long time. We have purified a multimeric [FeFe]-
hydrogenase
from A. woodii containing four subunits (HydABCD) which is predicted to have one [H]-cluster, three [2Fe2S]-, and six [4Fe4S]-clusters consistent with the experimental determination of 32 mol of Fe and 30 mol of acid-labile sulfur. The enzyme indeed catalyzed hydrogen-based ferredoxin reduction, but required NAD(+) for this reaction. NAD(+) was also reduced but only in the presence of ferredoxin. NAD(+) and ferredoxin reduction both required flavin. Spectroscopic analyses revealed that NAD(+) and ferredoxin reduction are strictly coupled and that they are reduced in a 1:1 stoichiometry. Apparently, the multimeric
hydrogenase
of A. woodii is a soluble energy-converting
hydrogenase
that uses electron bifurcation to drive the endergonic ferredoxin reduction by coupling it to the exergonic NAD(+) reduction.
...
PMID:A bacterial electron-bifurcating hydrogenase. 2281 Feb 30
Hydrogenases are key enzymes of the energy metabolism of many microorganisms. Especially in anoxic habitats where molecular hydrogen (H
2
) is an important intermediate, these enzymes are used to expel excess reducing power by reducing protons or they are used for the oxidation of H
2
as energy and electron source. Despite the fact that hydrogenases catalyze the simplest chemical reaction of reducing two protons with two electrons it turned out that they are often parts of multimeric enzyme complexes catalyzing complex chemical reactions with a multitude of functions in the metabolism. Recent findings revealed multimeric hydrogenases with so far unknown functions particularly in bacteria from the class Clostridia. The discovery of [FeFe] hydrogenases coupled to electron bifurcating subunits solved the
enigma
of how the otherwise highly endergonic reduction of the electron carrier ferredoxin can be carried out and how H
2
production from NADH is possible. Complexes of [FeFe] hydrogenases with formate dehydrogenases revealed a novel enzymatic coupling of the two electron carriers H
2
and formate. These novel
hydrogenase
enzyme complex could also contribute to biotechnological H
2
production and H
2
storage, both processes essential for an envisaged economy based on H
2
as energy carrier.
...
PMID:Complex Multimeric [FeFe] Hydrogenases: Biochemistry, Physiology and New Opportunities for the Hydrogen Economy. 3056 6
