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)

In the analysis of an ethanol-CO(2) enrichment of bacteria from an anaerobic sewage digestor, a strain tentatively identified as Desulfovibrio vulgaris and an H(2)-utilizing methanogen resembling Methanobacterium formicicum were isolated, and they were shown to represent a synergistic association of two bacterial species similar to that previously found between S organism and Methanobacterium strain MOH isolated from Methanobacillus omelianskii. In lowsulfate media, the desulfovibrio produced acetate and H(2) from ethanol and acetate, H(2), and, presumably, CO(2) from lactate; but growth was slight and little of the energy source was catabolized unless the organism was combined with an H(2)-utilizing methanogenic bacterium. The type strains of D. vulgaris and Desulfovibrio desulfuricans carried out the same type of synergistic growth with methanogens. In mixtures of desulfovibrio and strain MOH growing on ethanol, lactate, or pyruvate, diminution of methane produced was stoichiometric with the moles of sulfate added, and the desulfovibrios grew better with sulfate addition. The energetics of the synergistic associations and of the competition between the methanogenic system and sulfate-reducing system as sinks for electrons generated in the oxidation of organic materials such as ethanol, lactate, and acetate are discussed. It is suggested that lack of availability of H(2) for growth of methanogens is a major factor in suppression of methanogenesis by sulfate in natural ecosystems. The results with these known mixtures of bacteria suggest that hydrogenase-forming, sulfate-reducing bacteria could be active in some methanogenic ecosystems that are low in sulfate.
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PMID:Growth of desulfovibrio in lactate or ethanol media low in sulfate in association with H2-utilizing methanogenic bacteria. 87 75

The products of glucose fermentation were studied in 87 strains of the genus Chlorella. Lactic acid, acetic acid, formic acid, glycerol, ethanol, H2 and CO2 were identified. The lactic acid was shown to be D(minus)lactic acid. The pattern of fermentation produces is species-specific and can therefore be used as a taxonomic character. Lactic acid was found in C. fusca (varieties vacuolata, fusca, and rubescens), C. zofingiensis, C. vulgaris (var. vulgaris and f.tertia), and C. protothecoides. Formic acid and H2 appeared in those species which contain hydrogenase. Rather large amounts of glycerol were produced only by the most salt-tolerant species C. luteoviridis, C. saccharophila, and C. protothecoides.
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PMID:Physiological and biochemical contributions to the taxonomy of the genus Chlorella. X. Products of glucose fermentation. 115 86

The microaerophilic protozoon Trichomonas vaginals responds to extracellular changes in oxygen concentration: acetate, lactate, ethanol, H2 and CO2 formation, as well as glucose-depletion rates, are affected. All these variables except ethanol production rates, also differed between clinically metronidazole-sensitive (1910) and resistant (IR78 and CDC85) strains. Most interesting were the greatly increased glucose-scavenging rates of resistant isolates and their low specific activities of hydrogenase and H2 formation rates by comparison with the metronidazole-sensitive strain. Results suggest that all three strains of this parasite are well adapted to the O2 levels prevailing in situ (13-56 microM). Thus, vaginal oxygen tensions have more pronounced effects on the balances of fermentation products in the resistant strains, and results indicate that these strains may then use hydrogenosomal pathways to their advantage.
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PMID:Influence of oxygen on the fermentative metabolism of metronidazole-sensitive and resistant strains of Trichomonas vaginalis. 147 4

Spirochaeta thermophila RI 19.B1 (DSM 6192) fermented glucose to lactate, acetate, CO2, and H2 with concomitant formation of cell material. The cell dry mass yield was 20.0 g/mol of glucose. From the fermentation balance data and knowledge of the fermentation pathway, a YATP of 9.22 g of dry mass per mol of ATP was calculated for pH-uncontrolled batch-culture growth on glucose in a mineral medium. Measurement of enzyme activities in glucose-grown cells revealed that glucose was taken up by a permease and then subjected to ATP-dependent phosphorylation by a hexokinase. Glucose-6-phosphate was further metabolized to pyruvate through the Embden-Meyerhof-Parnas pathway. The phosphoryl donor for phosphofructokinase activity was PPi rather than ATP. This was also found for the type strain of S. thermophila, Z-1203 (DSM 6578). PPi was probably formed by pyrophosphoroclastic cleavage of ATP, with recovery of the resultant AMP by the activity of adenylate kinase. All other measured kinase activities utilized ATP as the phosphoryl donor. Pyruvate was further metabolized to acetyl coenzyme A with concomitant production of H2 and CO2 by pyruvate synthase. Lactate was also produced from pyruvate by a fructose-1,6-diphosphate-insensitive lactate dehydrogenase. Evidence was obtained for the transfer of reducing equivalents from the glycolytic pathway to hydrogenase to produce H2. No formate dehydrogenase or significant ethanol-producing enzyme activities were detected.
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PMID:Glucose catabolism by Spirochaeta thermophila RI 19.B1. 155 64

The response of the membrane-associated carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum to solubilization by detergents and organic solvents, the properties of solubilized CODH, and the mechanism for coupling CO oxidation to hydrogen evolution via a CO-induced hydrogenase activity have been investigated. The release of CODH by a variety of ionic and nonionic detergents occurs in a redox-dependent fashion: CODH is solubilized in the presence of low-potential reductants (dithionite, CO, and H2) but is resistant to solubilization from membranes prepared in the absence of reductant or membranes prepared in the presence of reductant and subsequently dye-oxidized. This redox-dependent response to detergent solubilization has been exploited to release CODH from the membranes in a purified state. CODH can also be solubilized from deoxycholate-washed membranes in a redox-independent manner with 20% ethanol. CODH solubilized by deoxycholate or ethanol, when purified to homogeneity by the protocol previously described for heat-solubilized CODH (Bonam, D., and Ludden, P. W. (1987) J. Biol. Chem. 262, 2980-2987), is associated with a previously unobserved 22-kDa protein. The 22-kDa protein can be dissociated from CODH with acetonitrile and can be reconstituted with CODH, after removal of acetonitrile, in a stoichiometric (1:1) fashion. The isolated 22-kDa protein contained 4.0 iron atoms, a reducible Fe-S center, and was O2- and heat-labile. The 22-kDa protein did not alter the catalytic properties of CODH as assayed in vitro with methyl viologen as the electron acceptor for CO oxidation, but was required for reconstituting CO oxidation to hydrogen evolution via the CO-induced membrane-bound hydrogenase. Other electron carrier proteins (ferredoxins and flavodoxin) were ineffective at coupling CO oxidation and hydrogen evolution. We conclude that the 22-kDa protein is a reversibly dissociable subunit of CODH tha mediates electron transfer to hydrogenase.
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PMID:Characterization of the CO oxidation/H2 evolution system of Rhodospirillum rubrum. Role of a 22-kDa iron-sulfur protein in mediating electron transfer between carbon monoxide dehydrogenase and hydrogenase. 191 63

Fermenting anaerobic cultures of Escherichia coli were observed by the nonintrusive technique of in vivo, whole-culture nuclear magnetic resonance. Fermentation balances were calculated for hexoses, pentoses, sugar alcohols, and sugar acids. Substrates more reduced than glucose yielded more of the highly reduced fermentation product ethanol, whereas more-oxidized substrates produced more of the less-reduced fermentation product acetate. These relationships were made more obvious by the introduction of ldhA mutations, which abolished lactate production, and delta frd mutations, which eliminated succinate. When grown anaerobically on sugar alcohols such as sorbitol, E. coli produced ethanol in excess of the amount calculated by the standard fermentation pathways. Reducing equivalents must be recycled from formate to account for this excess of ethanol. In mutants deficient in hydrogenase (hydB), ethanol production from sorbitol was greatly decreased, implying that hydrogen gas released from formate by the formate-hydrogen lyase system may be partially recycled, in the wild type, to increase the yield of the highly reduced fermentation product ethanol.
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PMID:Anaerobic fermentation balance of Escherichia coli as observed by in vivo nuclear magnetic resonance spectroscopy. 268 Nov 56

The effects of alcohols on the reactivity of Azotobacter vinelandii hydrogenase were investigated. Hydrogenase catalyzed H2 oxidation coupled to methylene blue, benzyl viologen, or phenazine methosulfate when in the presence of solvents containing 15 or 40% ethanol or 40% methanol or 2-propanol. In general, the Km's for the electron acceptors were increased substantially by the presence of the alcohols, while the Km for H2 was not altered in a solvent containing 40% ethanol. Calculation of the apparent maximum velocities for H2 oxidation in the presence of alcohols indicated that the maximum velocity was not decreased in most cases. In contrast, the rates of both H2 evolution and isotope exchange by hydrogenase were substantially decreased when solvent containing alcohol. Hydrogenase was inactivated by 100% ethanol with a half-life of 17 s. Hydrogenase from A. vinelandii was stable when stored in alcohol/buffer solvents at 20 degrees C or below. However, the thermal stability of hydrogenase was greatly decreased by inclusion of an alcohol in the solvent. When incubated at 55 degrees C in a solvent containing 40% ethanol, activity decreased in a first-order process with a half-life of 7 min. When incubated at the same temperature in aqueous buffer, no loss of activity was observed over 30 min.
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PMID:Effects of alcohols on the reactivity and stability of Azotobacter vinelandii hydrogenase. 327 40

The metabolic and enzymatic bases for growth tolerance to ethanol (4%) and H2 (2 atm [1 atm = 101.29 kPa]) fermentation products in Clostridium thermohydrosulfuricum were compared in a sensitive wild-type strain and an insensitive alcohol-adapted strain. In the wild-type strain, ethanol (4%) and H2 (2 atm) inhibited glucose but not pyruvate fermentation parameters (growth and end product formation). Inhibition of glucose fermentation by ethanol (4%) in the wild-type strain was reversed by addition of acetone (1%), which lowered H2 and ethanol production while increasing isopropanol and acetate production. Pulsing cells grown in continuous culture on glucose with 5% ethanol or 1 atm of H2 significantly raised the NADH/NAD ratio in the wild-type strain but not in the alcohol-adapted strain. Analysis of key oxidoreductases demonstrated that the alcohol-adapted strain lacked detectable levels of reduced ferredoxin-linked NAD reductase and NAD-linked alcohol dehydrogenase activities which were present in the wild-type strain. Differences in the glucose fermentation product ratios of the two strains were related to differences in lactate dehydrogenase and hydrogenase levels and sensitivity of glyceraldehyde 3-phosphate dehydrogenase activity to NADH inhibition. A biochemical model is proposed which describes a common enzymatic mechanism for growth tolerance of thermoanaerobes to moderate concentrations of both ethanol and hydrogen.
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PMID:Ethanol production by thermophilic bacteria: biochemical basis for ethanol and hydrogen tolerance in Clostridium thermohydrosulfuricum. 337 83

Detailed physiological studies were done to compare the influence of environmental pH and fermentation end product formation on metabolism, growth, and proton motive force in Sarcina ventriculi. The kinetics of end product formation during glucose fermentation in unbuffered batch cultures shifted from hydrogen-acetate production to ethanol production as the medium pH dropped from 7.0 to 3.3. At a constant pH of 3.0, the production of acetate ceased when the accumulation of acetate in the medium reached 40 mmol/liter. At a constant pH of 7.0, acetate production continued throughout the entire growth time course. The in vivo hydrogenase activity was much higher in cells grown at pH 7.0 than at pH 3.0. The magnitude of the proton motive force increased in relation to a decrease of the medium pH from 7.5 to 3.0. When the organism was grown at pH 3.0, the cytoplasmic pH was 4.25 and the organism was unable to exclude acetic acid or butyric acid from the cytoplasm. Addition of acetic acid, but not hydrogen or ethanol, inhibited growth and resulted in proton motive force dissipation and the accumulation of acetic acid in the cytoplasm. The results indicate that S. ventriculi is an acidophile that can continue to produce ethanol at low cytoplasmic pH values. Both the ability to shift to ethanol production and the ability to continue to ferment glucose while cytoplasmic pH values are low adapt S. ventriculi for growth at low pH.
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PMID:Physiological adaptations of anaerobic bacteria to low pH: metabolic control of proton motive force in Sarcina ventriculi. 357 Nov 64

The butyrate analogue 2-bromobutyrate is toxic toward Clostridium acetobutylicum. After mutation using nitrosoguanidine, mutants resistant to the suicide co-substrate 2-bromobutyrate were selected. Such mutants no longer produced acetone, whereas the synthesis of butanol and ethanol was unaffected. Enzymatic analysis of a 2-bromobutyrate-resistant mutant showed a low level of coenzyme A transferase and of acetoacetate decarboxylase, the two enzymes implicated in the biosynthesis of acetone, whereas the level of hydrogenase was unaffected.
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PMID:[Selection of mutants of Clostridium acetobutylicum defective in production of acetone]. 362 Feb 1


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