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)

Sulfate-reducing bacteria, Desulfovibrio vulgaris, strain Miyazaki, were grown on either sulfate, sulfite, or thiosulfate as the terminal electron acceptor. Better growth was observed on sulfite and less growth on thiosulfate than on sulfate. Enzyme levels of adenylylsulfate (APS) reductase [EC 1.8.99.2], reductant-activated inorganic pyrophosphatase [EC 3.6.1.1], sulfite reductase [EC 1.8.99.1] (desulfoviridin), hydrogenase [EC 1.12.2.1], and Mg2+-activated ATPase [EC 3.6.1.3] were compared in crude extracts of these cells at various stages of growth. 1) The specific activity of APS reductase in sulfite-grown cells was only one-fourth that in sulfate-grown cells throughout growth. Thiosulfate-grown cells had an activity intermediate between those of sulfate- and sulfite-grown cells. 2) Cells grown on sulfite had lower specific activity of reductant-activated inorganic pyrophosphatase than cells grown on sulfate or thiosulfate. 3) The specific activity of sulfite reductase (desulfoviridin) was highest in sulfite-grown cells. The sulfite medium gave the enzyme in high yield as well as with high specific activity. 4) The specific activities of hydrogenase and Mg2+-ATPase were not significantly altered by electron acceptors in the growth medium.
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PMID:Biochemical studies on sulfate-reducing bacteria. XIV. Enzyme levels of adenylylsulfate reductase, inorganic pyrophosphatase, sulfite reductase, hydrogenase, and adenosine triphosphatase in cells grown on sulfate, sulfite, and thiosulfate. 17 50

Both nickel-specific transport and nickel transport by a magnesium transporter have been described previously for a variety of nickel-utilizing bacteria. The derepression of hydrogenase activity in Bradyzhizobium japonicum JH and in a gene-directed mutant of strain JH (in an intracellular Ni metabolism locus), strain JHK7, was inhibited by MgSO4. For both strains, Ni2+ uptake was also markedly inhibited by Mg2+, and the Mg(2+)-mediated inhibition could be overcome by high levels of Ni2+ provided in the assay buffer. The results indicate that both B. japonicum strains transport Ni2+ via a high-affinity magnesium transport system. Dixon plots (1/V versus inhibitor) showed that the divalent cations Co2+, Mn2+, and Zn2+, like Mg2+, were competitive inhibitors of Ni2+ uptake. The KiS for nickel uptake inhibition by Mg2+, Co2+, Mn2+, and Zn2+ were 48, 22, 12, and 8 microM, respectively. Cu2+ strongly inhibited Ni2+ uptake, and molybdate inhibited it slightly. Respiratory inhibitors cyanide and azide, the uncoupler carbonyl cyanide m-chlorophenylhydrazone, the ATPase inhibitor N,N'-dicyclohexylcarbodiimide, and ionophores nigericin and valinomycin significantly inhibited short-term (5 min) Ni2+ uptake, showing that Ni2+ uptake in strain JH is energy dependent. Most of these conclusions are quite different from those reported previously for a different B. japonicum strain belonging to a different serogroup.
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PMID:Competitive inhibition of an energy-dependent nickel transport system by divalent cations in Bradyrhizobium japonicum JH. 178 26

Crossed immunoelectrophoresis was used to analyze the components of membrane vesicles of anaerobically grown Escherichia coli. The number of precipitation lines in the crossed immunoelectrophoresis patterns of membrane vesicles isolated from E. coli grown anaerobically on glucose plus nitrate and on glycerol plus fumarate were 83 and 70, respectively. Zymogram staining techniques were used to identify immunoprecipitates corresponding to nitrate reductase, formate dehydrogenase, fumarate reductase, and glycerol-3-phosphate dehydrogenase in crossed immunoelectrophoresis reference patterns. The identification of fumarate reductase by its succinate oxidizing activity was confirmed with purified enzyme and with mutants lacking or overproducing this enzyme. In addition, precipitation lines were found for hydrogenase, cytochrome oxidase, the membrane-bound ATPase, and the dehydrogenases for succinate, malate, dihydroorotate, D-lactate, 6-phosphogluconate, and NADH. Adsorption experiments with intact and solubilized membrane vesicles showed that fumarate reductase, hydrogenase, glycerol-3-phosphate dehydrogenase, nitrate reductase, and ATPase are located at the inner surface of the cytoplasmic membrane; on the other hand, the results suggest that formate dehydrogenase is a transmembrane protein.
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PMID:Identification and localization of enzymes of the fumarate reductase and nitrate respiration systems of escherichia coli by crossed immunoelectrophoresis. 621 54

The reduction of CO2 or any other methanogenic substrate to methane serves the same function as the reduction of oxygen, nitrate or sulfate to more reduced products. These exergonic reactions are coupled to the production of usable energy generated through a charge separation and a protonmotive-force-driven ATPase. For the understanding of how methanogens derive energy from C-1 unit reduction one must study the biochemistry of the chemical reactions involved and how these are coupled to the production of a charge separation and subsequent electron transport phosphorylation. Data on methanogenesis by a variety of organisms indicates ubiquitous use of CH3-S-CoM as the final electron acceptor in the production of methane through the methyl CoM reductase and of 5-deazaflavin as a primary source of reducing equivalents. Three known enzymes serve as catalysts in the production of reduced 5-deazaflavin: hydrogenase, formate dehydrogenase and CO dehydrogenase. All three are potential candidates for proton pumps. In the organisms that must oxidize some of their substrate to obtain electrons for the reduction of another portion of the substrate to methane (e.g., those using formate, methanol or acetate), the latter two enzymes may operate in the oxidizing direction. CO2 is the most frequent substrate for methanogenesis but is the only substrate that obligately requires the presence of H2 and hydrogenase. Growth on methanol requires a B12-containing methanol-CoM methyl transferase and does not necessarily need any other methanogenic enzymes besides the methyl-CoM reductase system when hydrogenase is present. When bacteria grow on methanol alone it is not yet clear if they get their reducing equivalents from a reversal of methanogenic enzymes, thus oxidizing methyl groups to CO2. An alternative (since these and acetate-catabolizing methanogens possess cytochrome b) is electron transport and possible proton pumping via a cytochrome-containing electron transport chain. Several of the actual components of the methanogenic pathway from CO2 have been characterized. Methanofuran is apparently the first carbon-carrying cofactor in the pathway, forming carboxy-methanofuran. Formyl-FAF or formyl-methanopterin (YFC, a very rapidly labelled compound during 14C pulse labeling) has been implicated as an obligate intermediate in methanogenesis, since methanopterin or FAF is an essential component of the carbon dioxide reducing factor in dialyzed extract methanogenesis. FAF also carries the carbon at the methylene and methyl oxidation levels.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The bioenergetics of methanogenesis. 623 47

Male inbred Fischer rats were fed a diet containing 5 p.p.m. aflatoxin for 1, 3, 4 1/2 and 6 weeks at which times groups were killed for histological and histochemical study. Aflatoxin produced a scattered individual cell necrosis of parenchymal cells by 1 week. At 3 weeks small basophilic proliferative foci were seen which increased in size and abundance to 6 weeks. These foci showed starvation-resistant glycogen, variable depletion of glucose-6-phosphatase, succinic dehydrogenase, aniline hydrogenase, membrane ATPase and acid phosphatase. At 6 weeks the foci showed the presence of gamma glutamyl transpeptidase and glucose-6-phosphate dehydrogenase. The basophilic foci were not preceded by other focal histological and histochemical change. The basophilic proliferative lesions are observed when an irreversible change has been induced in the liver. The role of such lesions in the histogenesis of hepatocellular carcinoma is discussed.
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PMID:Histochemical studies on the early proliferative lesion induced in the rat liver by aflatoxin. 724 Dec 69

The syntrophically glycolate-fermenting bacterium in the methanogenic binary coculture FlGlyM was isolated in pure culture (strain FlGlyR) with glyoxylate as sole substrate. This strain disproportionated 12 glyoxylate to 7 glycolate, 10 CO2, and 3 hydrogen. Glyoxylate was oxidized via the malyl-CoA pathway. All enzymes of this pathway, i.e. malyl-CoA lyase/malate: CoA ligase, malic enzyme, and pyruvate synthase, were demonstrated in cell-free extracts. Glycolate dehydrogenase, hydrogenase, and ATPase, as well as menaquinones as potential electron carriers, were present in the membranes. Everted membrane vesicles catalyzed hydrogen-dependent glyoxylate reduction to glycolate [86-207 nmol min-1 (mg protein)-1] coupled to ATP synthesis from ADP and Pi [38-82 nmol min-1 (mg protein)-1)]. ATP synthesis was abolished entirely by protonophores or ATPase inhibitors (up to 98 and 94% inhibition, respectively) indicating the involvement of proton-motive force in an electron transport phosphorylation driven by a new glyoxylate respiration with hydrogen as electron donor. Measured reaction rates in vesicle preparations revealed a stoichiometry of ATP formation of 0.2-0.5 ATP per glyoxylate reduced.
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PMID:Electron transport phosphorylation driven by glyoxylate respiration with hydrogen as electron donor in membrane vesicles of a glyoxylate-fermenting bacterium. 776 34

We have sequenced downstream of the last previously sequenced gene of the glucitol operon (gutABDMRQ) in E. coli and have found that gutQ is the last gene of this operon. Downstream of the gutQ gene is found a palindromic unit (PU or REP sequence), followed by a large open reading frame of 1515 (or possibly 1590) bps transcribed in the direction opposite to that of the gut operon. This open reading frame encodes a protein of 504 (or possibly 529) amino acids with a tripartite structure. The N-terminal "receiver" domain of 187 (or possibly 212) residues is homologous to the FhlA protein of E. coli, a transcriptional activator of formate hydrogen lyase. It may possess a short domain at its extreme N-terminus exhibiting sequence similarity to carbohydrate binding proteins. The central ATPase domain (236 residues) exhibits greatest sequence similarity to the HydG protein of E. coli, a transcriptional activator of labile hydrogenase. The C-terminal DNA binding domain (81 residues) is homologous to NtrX of Azorhizobium caulinodans, a protein involved in transcriptional regulation of nitrogen fixation. Sequence comparisons with well-characterized transcription factors suggest that ORF504 encodes a protein that hydrolyzes ATP to generate the open transcriptional initiation complex of sigma 54-dependent promoters, possibly in response to redox conditions and/or ligand binding. We propose that this tripartite transcription factor arose by fusion of gene fragments encoding its three constituent modules.
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PMID:DNA sequence of a gene in Escherichia coli encoding a putative tripartite transcription factor with receiver, ATPase and DNA binding domains. 789 55

It is shown that -2H+/K(+)-exchange through the H(+)-K(+)-pump, formed by the F0F1-ATPase and the Trk H system, H(+)-K(+)-exchange via H(+)-K(+)-antiporter, formed by the F0 and the Trk G (core) system [1-2], and production of H2 in anaerobically grown E.coli are changed in the mutants with defects in components of formate hydrogen lyase complex, oxidizing formate to CO2 and H2. 2H+/K(+)-exchange and H2 production are destroyed, but H(+)-K(+)-exchange with a variable stoichiometry for N,N'-dicyclohexyl-carbodiimide-sensitive ion fluxes is displayed in the fdhF mutant E.coli FM911, where formate dehydrogenase(H) is absent. 2H+/K(+)-exchange does not occur, but H(+)-K(+)-exchange with variable stoichiometry for N,N'-dicyclohexylcarbodiimide-sensitive ion fluxes and H2 production are observed in the uncD mutant E.coli AN817 with defect in beta subunit of the F1. Deletion of the hyc-operon in mutant E.coli HD700, led to absence of hydrogenase 3, destroys H(+)-K(+)-exchange and H2 production. H2 evaluation is shown in the E.coli K12(lambda) protoplasts, treated with toluene, by adding of NADH into the medium, containing ATP and K+. It is inhibited by N,N'-dicyclohexylcarbodiimide. H2 production is increased by adding of dithiothreitol, when NADH is changed by formate. It is lost in the mutants with defects in the F0 (E.coli AN936) or in the Trk A protein (E.coli TK2242). Dehydrogenase(H) and hydrogenase 3 are assumed to link mutually with a H(+)-K(+)-pump operation, reducing equivalents, necessary for a dithiol-disulfide interconversion within a mechanism of pump, are transferred from formate by means of dehydrogenase(H) to hydrogenase 3 through the F0F1 and the Trk H system to produce H2. It is assumed that hydrogenase 3 can interact with a mechanism of H(+)-K(+)-antiporter, NADH could serve as a donor of reducing equivalents. A role of thiol-groups and dithiol-disulfide interconversion in a functions of both mechanism for H(+)-K(+)-exchange is confirmed.
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PMID:[Role of components of formate-hydrogen-lyase in forming molecular hydrogen and their connection with proton-potassium exchange in anaerobically grown Escherichia coli]. 872 54

The growth of the syntrophic propionate-oxidizing bacterium strain MPOB in pure culture by fumarate disproportionation into carbon dioxide and succinate and by fumarate reduction with propionate, formate or hydrogen as electron donor was studied. The highest growth yield, 12.2 g dry cells/mol fumarate, was observed for growth by fumarate disproportionation. In the presence of hydrogen, formate or propionate, the growth yield was more than twice as low: 4.8, 4.6, and 5.2 g dry cells/mol fumarate, respectively. The location of enzymes that are involved in the electron transport chain during fumarate reduction in strain MPOB was analyzed. Fumarate reductase, succinate dehydrogenase, and ATPase were membrane-bound, while formate dehydrogenase and hydrogenase were loosely attached to the periplasmic side of the membrane. The cells contained cytochrome c, cytochrome b, menaquinone-6 and menaquinone-7 as possible electron carriers. Fumarate reduction with hydrogen in membranes of strain MPOB was inhibited by 2-(heptyl)-4-hydroxyquinoline-N-oxide (HOQNO). This inhibition, together with the activity of fumarate reductase with reduced 2,3-dimethyl-1,4-naphtoquinone (DMNH2) and the observation that cytochrome b of strain MPOB was oxidized by fumarate, suggested that menequinone and cytochrome b are involved in the electron transport during fumarate reduction in strain MPOB. The growth yields of fumarate reduction with hydrogen or formate as electron donor were similar to the growth yield of Wolinella succinogenes. Therefore, it can be assumed that strain MPOB gains the same amount of ATP from fumarate reduction as W. succinogenes, i. e. 0.7 mol ATP/mol fumarate. This value supports the hypothesis that syntrophic propionate-oxidizing bacteria have to invest two-thirds of an ATP via reversed electron transport in the succinate oxidation step during the oxidation of propionate. The same electron transport chain that is involved in fumarate reduction may operate in the reversed direction to drive the energetically unfavourable oxidation of succinate during syntrophic propionate oxidation since (1) cytochrome b was reduced by succinate and (2) succinate oxidation was similarly inhibited by HOQNO as fumarate reduction.
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PMID:Investigation of the fumarate metabolism of the syntrophic propionate-oxidizing bacterium strain MPOB. 953 36

Elemental sulfur reduction by the hyperthermophilic bacterium Thermotoga neapolitana provides an alternative to hydrogen evolution during fermentation. Electrons are transferred from reduced cofactors (ferredoxin and NADH) to sulfur by a series of unknown steps. One enzyme that may be involved is an NADH:methyl viologen oxidoreductase (NMOR), an activity that in other fermenting organisms is associated with NADH:ferredoxin oxidoreductase. We found that 83% of NMOR activity was contained in the pellet fraction of cell extracts subjected to ultracentrifugation. This pellet fraction, presumably containing cell membranes, was required for electron transfer to NAD+ from ferredoxin-dependent pyruvate oxidation. However, the NMOR activity in this fraction used neither Thermotoga nor clostridial ferredoxins as substrates. NMOR activity was also detected in aerobically prepared vesicles. By comparison with ATPase activities, NMOR was found primarily on the cytoplasmic face of these vesicles. During these studies, an extracytoplasmic hydrogenase activity was discovered. In contrast to the soluble hydrogenase, this hydrogenase activity was completely inhibited when intact cells were treated with cupric chloride and was present on the extracytoplasmic face of vescides. In contrast to a soluble hydrogenase reported in Thermotoga maritima, this activity was air-stable and was inhibited by low concentrations of nitrite.
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PMID:Membrane-associated redox activities in Thermotoga neapolitana. 973 44


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