Bacterial hydrogenase

At present, several stable photocatalytic systems for production of hydrogen from water and organic compounds are made of semiconducting oxides and suitable proton reducing catalyzer. An efficient electron transfer between inorganic semiconductor and bacterial hydrogenase was shown to result in hydrogen photoproduction. 

V. V. Nikandrov, M. A. Shlyk, N. A. Zorin, I. N. Gogotov, A. A. Krasnovsky (1988) Efficient photoinduced electron transfer from inorganic semiconductor Ti02 to bacterial hydrogenase. FEBSLett., 234 111-114... 

Ni2 + bound to deprotonated peptide nitrogens in tri- and tetrapeptides can be oxidized to Ni3+ [331-333]. The presence of Ni3+ has been reported in bacterial hydrogenases and dehydrogenases [334, 335], which suggests a biological role for the Ni3 + /Ni2+ redox couple. 

Artificial cell-free systems have been investigated, to test models of photosynthetic production of H2. Benemann et al. (1973) demonstrated that it was possible to produce H2 and O2 by combining chloroplasts from green plants and bacterial hydrogenase, with ferredoxin as the intermediate electron carrier ... 

Nikandrov, V.V., Shlyk, M.A., Zorin, N.A., Gogotov, I.N., Krosnovsky, A.A. 1988. Efficient pho-toinduced electron-transfer from inorganic semiconductor TiO, to bacterial hydrogenase. Eebs Lett 234 111-114. 

Hydrogen Molecular hydrogen metabolized by some bacteria Constituent of water and all organic molecules. DjO is toxic to mammals. Bacterial hydrogenases are nrckd-containirg enzymes/... 

Although the spectra of oxidized bacterial and plant ferredoxins are different, Fig. 4 shows that, when reduced, their absorption spectra are remarkably similar. In both cases, the absorbancy peaks in the visible region disappear, while there is little change in ultraviolet absorption. In Fig. 4 the ferredoxins were reduced by hydrogen gas with a bacterial hydrogenase preparation. When air was admitted into the cuvettes, both ferredoxins were auto-oxidized and showed their original absorption spectra (Fig. 3). Ferredoxins, therefore, are like cytochrome c in that reduction and oxidation is a reversible process. However, unlike the cytochromes, the ferredoxins are colored in the oxidized state and colorless when reduced. 

As pointed out previously, illuminated chloroplast fragments are convenient for reducing ferredoxin and, in the presence of the appropriate enzymes, photoreduced ferredoxin can be used in processes that may have nothing to do with green plants. For example, in the presence of bacterial hydrogenase, photoreduced ferredoxin is used for the evolution of hydrogen gas (Tagawa and Arnon (99)) and, in the presence of other bacterial enzymes, it is used for reductive carboxylation reactions (Bachofen, Buchanan, and Arnon (13) Buchanan and Evans (30)). 

A number of low-molecular-weight inorganic ligands are involved in metal binding in metalloproteins. These include HCO) and P04, as ligands to Fe in proteins involved in iron transport, in association with amino acid residues of the protein. We will discuss the role of CN and CO as ligands to Fe in bacterial hydrogenases, where they are part of more complex metal centres in a later section. 

Bacterial hydrogenase Montmorillonite nanoparticles Modified electrodes [52]... 

The photochemical apparatus of chloroplasts can be used under certain conditions to generate gaseous hydrogen, a direct proof of the photolysis of water. For this demonstration, the primarj redox system ferredoxin has to be coupled with a bacterial hydrogenase, which transfers electrons from Fe++ onto H+ leaving ferredoxin-Fe+++ and i H2. 

Krasnovsky AA, Chan Van Ni, Nikandrov VV and Brin GP (1980) Efficiency of hydrogen photoproduction by chloroplast-bacterial hydrogenase systems. Plant Physiol. 66, 925-930. 

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