Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.12.7.2 (hydrogenase)
 3,522 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Crude extracts of a variety of Clostridium species reduce aromatic and aliphatic nitro compounds in the presence of hydrogen gas. Using different Clostridia, the uptake of hydrogen by p-nitrobenzoate is about 5--10 times faster than by 2-nitroethanol. Structurally rather different aliphatic nitro compounds show rates which differ by less than a factor of 3. Hydrogenase from Clostridium kluyveri and ferredoxins from Clostridium spec. La 1 and spinach have been purified. The combinations of the hydrogenase and each one of the ferredoxins catalyse the hydrogen uptake by nitro compounds. Clostridial flavodoxin also transfer electrons onto nitro compounds. Nitroaryl and nitroalkyl compounds behave differently with ferredoxin. The first reduction step (1-electron transfer) of p-nitrobenzoate leads to the nitro radical anion which can be detected by EPR measurements. Nitro alkanes seem to form a rather unstable radical which decomposes partially to form nitrite. Furthermore, 2-(N-hydroxyimino)- and 2-(N-hydroxyamino)ethanol, a nitrogen radical of 2-(N-hydroxyamino)ethanol as well as glycol and 1,4-butanediol were detected as intermediates and side products during the reduction of 2-nitro-ethanol to 2-aminoethanol. While the hydrogenase from Clostridium kluyveri seems not to be affected by any reduction intermediate, the ferredoxin from Clostridium spec. La 1 is inactivated by nitrite in a few minutes. Ferrous and sulfide ions in concentrations substoichiometric to that of nitrite stabilize and even reactivate the ferredoxin in the presence of 2-mercaptoethanol. A mechanism for the reduction of aliphatic nitro compounds catalysed by hydrogenase and ferredoxin is proposed.
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PMID:On the reduction of aliphatic and aromatic nitro compounds by Clostridia, the role of ferredoxin and its stabilization. 631 11

Ethanolamine was examined as a nitrogen source in the production of hydrogen by Rhodobacter capsulatus ST-410, a hydrogenase-deficient mutant of the strain B-100. It was found that ethanolamine supports cell growth as the sole nitrogen source and permits a large amount of hydrogen evolution, detected at 138 micromol/ml-culture from 3.5 mM ethanolamine and 30 mM DL-malate. The amount corresponded to a stoichiometric yield of 77% and was close to that obtained from 7.0 mM L-glutamate and 30 mM DL-malate. The hydrogen evolution rate per unit biomass (cells) was higher than that with L-glutamate, and the cells grown with ethanolamine had higher nitrogenase activity than the cells grown with L-glutamate. In terms of bioconversion of cellulosic and hemicellulosic biomass to hydrogen, D-glucose, D-xylose, and D-cellobiose were tested as substrates. The results indicated that those sugars permit a large evolution of hydrogen through cultivation with ethanolamine as a nitrogen source. For instance, the cells grown with 3.5 mM ethanolamine evolved hydrogen of 289 micromol/ml-culture (80% yield) from 30 mM D-glucose under a controlled pH of 6.4 to 6.9.
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PMID:Effects of Ethanolamine as a nitrogen source on hydrogen production by Rhodobacter capsulatus. 1073 77