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

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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)

Spinach chloroplast preparations were mixed with Clostridium kluyveri hydrogenase and ferredoxin. Hydrogen evolution could be measured in the light in the absence of any added electron donors. Inhibition of the water-splitting reaction or of photosystem II reduced the amount of H(2) evolved more than 95%, indicating that H(2)O was the electron donor in this reaction. The rates of H(2) evolution observed were up to 20% of those measured in the presence of an oxygen-consuming reaction or of photosystem I electron donors. These findings indicate that hydrogen evolution from water and sunlight by photosynthetic processes could be a method for solar energy conversion.
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PMID:Hydrogen evolution by a chloroplast-ferredoxin-hydrogenase system. 1659 4

We demonstrated that a significant volume of H(2) gas could be photobiologically produced by a marine green alga Platymonas subcordiformis when an uncoupler of photophosphorylation, carbonyl cyanide m-chlorophenylhydrazone (CCCP), was added after 32 h of anaerobic dark incubation, whereas a negligible volume of H(2) gas was produced without CCCP. The role of CCCP in enhancing photobiological H(2) production was delineated. CCCP as an ADRY agent (agent accelerating the deactivation reactions of water-splitting enzyme system Y) rapidly inhibited the photosystem II (PSII) activity of P. subcordiformis cells, resulting in a markedly decline in the coupled oxygen evolution. The mitochondrial oxidative respiration was only slightly inactivated by CCCP, which depleted O(2) in the light. As a result, anaerobiosis during the stage of photobiological H(2) evolution was established, preventing severe O(2) inactivation of the reversible hydrogenase in P. subcordiformis. The uncoupling effect of CCCP accelerates electron transfer from water due to a disruption of the proton motive force and release of DeltapH across the thylakoid membrane and thus enhances the accessibility of electron and H(+) to hydrogenase. The electrons for hydrogen photoevolution are mainly from the photolysis of water (90%). Upon the addition of CCCP, Chl a/b ratio increased, which implies a decrease in the light-harvesting PSII antennae or an increase in PSII/PSI ratio, possibly resulting in higher efficiency of utilization of light energy. The enhancement of H(2) evolution by the addition of CCCP is mostly due to the combination of the above three mechanisms. However, the disruption of the proton gradient across the thylakoid membrane may prevent a sustained photobiological H(2) evolution due to a shortfall of ATP generation essential for the maintenance and repair functions of the cells.
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PMID:Role of carbonyl cyanide m-chlorophenylhydrazone in enhancing photobiological hydrogen production by marine green alga Platymonas subcordiformis. 1659 59

A mass spectrometer inlet and an oxygen electrode in the same vessel allowed the continuous recording of the gases exchanged (H(2), CO(2), O(2)) by hydrogenase-containing anaerobically adapted Scenedesmus obliquus strain D(3) (Gaffron) and Chlorella fusca Shihira et Krauss (= pyrenoidosa) 211-15. A light intensity which produces more photosynthetic oxygen than the cells can re-reduce to water leads to de-adaptation and the substitution of normal photosynthesis for photoreduction. The sequence of these metabolic events was recorded in a matter of a few minutes. Upon exposure of these adapted algae to light, an evolution of hydrogen lasting up to 60 seconds preceded any other light-dependent gas exchange. In the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, this initial hydrogen production was inhibited approximately 50%, pointing to a contribution of electrons by photosystem II. At very low hydrogen tensions (0.1 microliter per milliliter), a balance between light-induced production and absorption of hydrogen was observed in normal, unpoisoned algae. Addition of either glucose or inhibitors of phosphorylation increased the release of hydrogen in the light very considerably. When the light was turned off the algae consumed the remaining amount of hydrogen, only to release it again upon illumination. This reversible hydrogen exchange persisted even when any concomitant carbon dioxide exchange had been abolished.
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PMID:The Gas Exchange of Hydrogen-adapted Algae as Followed by Mass Spectrometry. 1665 8

Dark H(2) metabolism was studied in marine and fresh water red algae, the green alga, Chlamydomonas, and mosses. A time variable and temperature-sensitive anaerobic incubation was required prior to H(2) evolution. H(2) evolution was sensitive to disalicylidenepropanediamine. An immediate H(2) uptake was observed in these algae. Immediate dark H(2) uptake but no evolution was observed in the mosses.A cell-free hydrogenase preparation was obtained from anaerobically adapted Chlamydomonas reinhardii by means of sonic oscillation. The hydrogenase was not sedimented at 100,000g. It catalyzed the reduction of methylene blue, p-benzoquinone, NAD, NADP, but not spinach ferredoxin. H(2) evolution was noted with dithionite and with reduced methyl viologen as donors but not with reduced spinach ferredoxin. Similarly, hydrogenase activities were not affected by disalicylidenepropanediamine. The pH optima for H(2) evolution and for H(2) uptake were 7.2 and 7.5 to 9.5, respectively. Extracts prepared from the anaerobically adapted red alga, Chondrus crispus, and the moss, Leptobryum pyriforme, consumed but did not evolve H(2). Uptake was slightly stimulated by methylene blue. It is proposed that red algae and mosses appear to metabolize H(2) by a different pathway than Chlamydomonas.
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PMID:H(2) metabolism in photosynthetic organisms: I. Dark h(2) evolution and uptake by algae and mosses. 1665 60

The water fern, Azolla caroliniana Willd., containing the symbiotic, heterocystous blue-green alga, Anabaena azollae, has been studied under various growth conditions to characterize its light-dependent production of H(2). The response of H(2) production to N(2) and C(2)H(2) and the absence of a differential effect of m-chlorocarbonyl cyanide phenylhydrazone on H(2) production and C(2)H(2) reduction, coupled with the parallel inhibition of both processes by DCMU imply that the production of H(2) is nitrogenase-catalyzed and ATP-dependent.H(2) was produced by fronds grown under air-CO(2) in the presence or absence of combined nitrogen. When cultured under argon-O(2)-CO(2), only those fronds provided with combined nitrogen remained viable and produced H(2). Fronds grown on nitrate under air plus 2% CO also produced H(2). In comparison to fronds grown on N(2) alone, fronds grown on nitrate had an increased rate of H(2) production relative to C(2)H(2) reduction, and the inhibition of H(2) production by air was less.CO in argon +/- CO(2) resulted in a partial inhibition of H(2) production, whereas CO in argon-CO(2)-C(2)H(2) enhanced H(2) production in fronds grown without combined nitrogen. Our studies strongly indicate that H(2) production is nitrogenase-catalyzed but the possibility that the symbiont contains a hydrogenase cannot be totally excluded.
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PMID:Azolla-Anabaena azollae Relationship: IV. Photosynthetically Driven, Nitrogenase-catalyzed H(2) Production. 1665 30

Gas-phase density functional theory calculations (B3LYP, double zeta plus polarization basis sets) are used to predict the solution-phase infrared spectra for a series of CO- and CN-containing iron complexes. It is shown that simple linear scaling of the computed C--O and C--N stretching frequencies yields accurate predictions of the the experimentally determined nu(CO) and nu(CN) values for a variety of complexes of different charges and in solvents of varying polarity. As examples of the technique, the resulting correlation is used to assign structures to spectroscopically observed but structurally ambiguous species in two different systems. For the (mu-SCH2CH2CH2S)[Fe(CO)3]2 complex in tetrahydrofuran solution, our calculations show that the initial electrochemical reduction process leads to a simple one-electron reduced product with a structure very similar to the (mu-SCH2CH2CH2S)[Fe(CO)3]2 parent complex. For the iron-iron hydrogenase enzyme active site, our computations show that the absence or presence of a water molecule near the distal iron center (the iron center further from the [4Fe4S] cluster and protein backbone) has very little effect on the predicted infrared spectra.
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PMID:Correlation between computed gas-phase and experimentally determined solution-phase infrared spectra: models of the iron-iron hydrogenase enzyme active site. 1680 76

Recent data depict membranes as the main sites where proteins/peptides are recruited and concentrated, misfold, and nucleate amyloids; at the same time, membranes are considered key triggers of amyloid toxicity. The N-terminal domain of the prokaryotic hydrogenase maturation factor HypF (HypF-N) in 30% trifluoroethanol undergoes a complex path of fibrillation starting with initial 2-3-nm oligomers and culminating with the appearance of mature fibrils. Oligomers are highly cytotoxic and permeabilize lipid membranes, both biological and synthetic. In this article, we report an in-depth study aimed at providing information on the surface activity of HypF-N and its interaction with synthetic membranes of different lipid composition, either in the native conformation or as amyloid oligomers or fibrils. Like other amyloidogenic peptides, the natively folded HypF-N forms stable films at the air/water interface and inserts into synthetic phospholipid bilayers with efficiencies depending on the type of phospholipid. In addition, HypF-N prefibrillar aggregates interact with, insert into, and disassemble supported phospholipid bilayers similarly to other amyloidogenic peptides. These results support the idea that, at least in most cases, early amyloid aggregates of different peptides and proteins produce similar effects on the integrity of membrane assembly and hence on cell viability.
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PMID:Natively folded HypF-N and its early amyloid aggregates interact with phospholipid monolayers and destabilize supported phospholipid bilayers. 1699 75

Although hydrogen is considered to be one of the most promising future energy sources and the technical aspects involved in using it have advanced considerably, the future supply of hydrogen from renewable sources is still unsolved. This review focuses on the production of hydrogen from water using biological catalysts that have been optimized by nature: the process of water-splitting photosynthesis on the one hand and hydrogen production via the catalyst hydrogenase on the other. Using water as a source of electrons and sunlight as a source of energy, both engineered natural systems and biomimetic (bio-inspired) model systems can be designed as first steps towards water-splitting-based hydrogen production (biophotolytic hydrogen production).
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PMID:Photosynthesis as a power supply for (bio-)hydrogen production. 1702 31

The ability of an eta2-H2 ligand to participate in intermolecular hydrogen bonding in solution has long been an unresolved issue. Such species are proposed to be key intermediates in numerous important reactions such as the proton-transfer pathway of H2 production by hydrogenase enzymes. We present the synthesis of several new water-soluble ruthenium coordination complexes including an eta2-H2 complex that is surprisingly inert to substitution by water. The existence of dihydrogen hydrogen bonding (DHHB) was experimentally probed by monitoring the chemical shift of H-bonded Ru-(H2) complexes using NMR spectroscopy, by UV-visible spectroscopy, and by monitoring the rotational dynamics of a hydrogen-bonding probe molecule. The results provide strong evidence that coordinated H2 can indeed participate in intermolecular hydrogen bonding to bulk solvent and other H-bond acceptors.
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PMID:Solution chemistry of a water-soluble eta2-H2 ruthenium complex: evidence for coordinated H2 acting as a hydrogen bond donor. 1714 94

The photobiological production of H2 gas, using water as the only electron donor, is a property of two types of photosynthetic microorganisms: green algae and cyanobacteria. In these organisms, photosynthetic water splitting is functionally linked to H(2) production by the activity of hydrogenase enzymes. Interestingly, each of these organisms contains only one of two major types of hydrogenases, [FeFe] or [NiFe] enzymes, which are phylogenetically distinct but perform the same catalytic reaction, suggesting convergent evolution. This idea is supported by the observation that each of the two classes of hydrogenases has a different metallo-cluster, is encoded by entirely different sets of genes (apparently under the control of different promoter elements), and exhibits different maturation pathways. The genetics, biosynthesis, structure, function, and O2 sensitivity of these enzymes have been the focus of extensive research in recent years. Some of this effort is clearly driven by the potential for using these enzymes in future biological or biohybrid systems to produce renewable fuel or in fuel cell applications.
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PMID:Hydrogenases and hydrogen photoproduction in oxygenic photosynthetic organisms. 1715 28


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