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)

The metabolism of Clostridium butyricum was manipulated at pH 6.5 and in phosphate-limited chemostat culture by changing the overall degree of reduction of the substrate using mixtures of glucose and glycerol. Cultures grown on glucose alone produced only acids (acetate, butyrate, and lactate) and a high level of hydrogen. In contrast, when glycerol was metabolized, 1,3-propanediol became the major product, the specific rate of acid formation decreased, and a low level of hydrogen was observed. Glycerol consumption was associated with the induction of (i) a glycerol dehydrogenase and a dihydroxyacetone kinase feeding glycerol into the central metabolism and (ii) an oxygen-sensitive glycerol dehydratase and an NAD-dependent 1,3-propanediol dehydrogenase involved in propanediol formation. The redirection of the electron flow from hydrogen to NADH formation was associated with a sharp decrease in the in vitro hydrogenase activity and the acetyl coenzyme A (CoA)/free CoA ratio that allows the NADH-ferredoxin oxidoreductase bidirectional enzyme to operate so as to reduce NAD in this culture. The decrease in acetate and butyrate formation was not explained by changes in the concentration of phosphotransacylases and acetate and butyrate kinases but by changes in in vivo substrate concentrations, as reflected by the sharp decrease in the acetyl-CoA/free CoA and butyryl-CoA/free CoA ratios and the sharp increase in the ATP/ADP ratio in the culture grown with glucose and glycerol compared with that in the culture grown with glucose alone. As previously reported for Clostridium acetobutylicum (L. Girbal, I. Vasconcelos, and P. Soucaille, J. Bacteriol. 176:6146-6147, 1994), the transmembrane pH of C. butyricum is inverted (more acidic inside) when the in vivo activity of hydrogenase is decreased (cultures grown on glucose-glycerol mixture). For both cultures, the stoichiometry of the H(+) ATPase was shown to remain constant and equal to 3 protons exported per molecule of ATP consumed.
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PMID:Regulation of carbon and electron flow in Clostridium butyricum VPI 3266 grown on glucose-glycerol mixtures. 1116 Jan 7

The main function of the hydrogenosome, a typical organelle of trichomonads, is to convert malate or pyruvate to H(2), CO(2) and acetate by a pathway associated with ATP synthesis. This pathway relies on activity of iron-sulfur proteins such as pyruvate:ferredoxin oxidoreductase (PFOR), hydrogenase and ferredoxin. To examine the effect of iron availability on proper hydrogenosomal function, the metabolic activity of the hydrogenosome and expression of hydrogenosomal enzymes were compared in Tritrichomonas foetus maintained under iron-rich (150 microM iron nitrilotriacetate) or iron-restricted (180 microM 2,2-dipyridyl) conditions in vitro. The activities of PFOR and hydrogenase, and also production of acetate and H(2), were markedly decreased or absent in iron-restricted trichomonads. Moreover, a decrease in activity of the hydrogenosomal malic enzyme, which is a non-Fe-S protein, was also observed. Impaired function of hydrogenosomes under iron-restricted conditions was compensated for by activation of the cytosolic pathway, mediating conversion of pyruvate to ethanol via acetaldehyde. This metabolic switch was fully reversible. Production of hydrogen by iron-restricted trichomonads was restored to the level of organisms grown under iron-rich conditions within 3 h after addition of 150 microM iron nitrilotriacetate. Protein analysis of purified hydrogenosomes from iron-restricted cells showed decreased levels of proteins corresponding to PFOR, malic enzyme and ferredoxin. Accordingly, these cells displayed decreased steady-state level and synthesis of mRNAs encoding PFOR and hydrogenosomal malic enzyme. These data demonstrate that iron is essential for function of the hydrogenosome, show its involvement in the expression of hydrogenosomal proteins and indicate the presence of iron-dependent control of gene transcription in Tt. foetus.
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PMID:Iron-induced changes in pyruvate metabolism of Tritrichomonas foetus and involvement of iron in expression of hydrogenosomal proteins. 1116 Aug

The amount of energy that can be conserved via halorespiration by Desulfitobacterium dehalogenans JW/IU-DC1 was determined by comparison of the growth yields of cells grown with 3-chloro-4-hydroxyphenyl acetate (Cl-OHPA) and different electron donors. Cultures that were grown with lactate, pyruvate, formate, or hydrogen as an electron donor and Cl-OHPA as an electron acceptor yielded 3.1, 6.6, 1.6, and 1.6 g (dry weight) per mol of reduction equivalents, respectively. Fermentative growth on pyruvate yielded 14 g (dry weight) per mol of pyruvate oxidized. Pyruvate was not fermented stoichiometrically to acetate and lactate, but an excess of acetate was produced. Experiments with 13C-labeled bicarbonate showed that during pyruvate fermentation, approximately 9% of the acetate was formed from the reduction of CO2. Comparison of the growth yields suggests that 1 mol of ATP is produced per mol of acetate produced by substrate-level phosphorylation and that there is no contribution of electron transport phosphorylation when D. dehalogenans grows on lactate plus Cl-OHPA or pyruvate plus Cl-OHPA. Furthermore, the growth yields indicate that approximately 1/3 mol of ATP is conserved per mol of Cl-OHPA reduced in cultures grown in formate plus Cl-OHPA and hydrogen plus Cl-OHPA. Because neither formate nor hydrogen nor Cl-OHPA supports substrate-level phosphorylation, energy must be conserved through the establishment of a proton motive force. Pyruvate ferredoxin oxidoreductase, lactate dehydrogenase, formate dehydrogenase, and hydrogenase were localized by in vitro assays with membrane-impermeable electron acceptors and donors. The orientation of chlorophenol-reductive dehalogenase in the cytoplasmic membrane, however, could not be determined. A model is proposed, which may explain the topology analyses as well as the results obtained in the yield study.
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PMID:Energy yield of respiration on chloroaromatic compounds in Desulfitobacterium dehalogenans. 1152 91

Major pathways of carbon and sulfur metabolisms were studied in representatives of two clusters of bacteria: Leucothrix thiophila (cluster I, strains 2WS, 4WS, and 6WS) and Leucothrix sp. (cluster II, strains 1WS, 3WS, and 5WS). All strains were capable of chemoorganoheterotrophic growth, as well as of chemolithoheterotrophic growth in the presence of reduced sulfur compounds. The bacteria were found to possess a complete set of the enzymes of the tricarboxylic acid cycle and glyoxylate cycle. The hydrogenase activity in cells of cluster I strains was an order of magnitude lower than in cluster II strains and in other known heterotrophic bacteria. Cells of bacteria of both clusters exhibited high activity levels of enzymes involved in the energy metabolism of sulfur. The oxidation of sulfur compounds and the operation of the electron-transport chain were shown to be related. Cluster II bacteria more efficiently use organic compounds in their energy metabolism, whereas cluster I bacteria are characterized by more efficient utilization of reduced sulfur compounds. During sulfite oxidation, cluster I bacteria can synthesize ATP both via substrate-level phosphorylation and oxidative phosphorylation, whereas cluster II bacteria synthesize ATP only via the latter process.
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PMID:[Carbon and sulfur metabolism in representatives of two clusters of bacteria of the genus Leucothrix: a comparative study]. 1213 49

HypF has been characterized as an auxiliary protein whose function is required for the synthesis of active [NiFe] hydrogenases in Escherichia coli and other bacteria. To approach the functional analysis, in particular the involvement in CO/CN ligand synthesis, HypF was purified from an overproducing strain to apparent homogeneity. The purified protein behaves as a monomer on size exclusion chromatography, and it is devoid of nickel or other cofactors. As indicated by the existence of a sequence motif also present in several O-carbamoyltransferases, HypF interacts with carbamoyl phosphate as a substrate and releases inorganic phosphate. In addition, HypF also possesses ATP cleavage activity that gives rise to AMP and pyrophosphate as products and that is dependent on the presence of carbamoyl phosphate. This and the fact that HypF catalyzes a carbamoyl phosphate-dependent pyrophosphate ATP exchange reaction suggest that the protein catalyzes activation of carbamoyl phosphate. Extensive mutagenesis of the putative functional motifs deduced from the derived amino acid sequence showed a full correlation of the resulting variants between their activity in hydrogenase maturation and the in vitro reactivity with carbamoyl phosphate. The results are discussed in terms of the involvement of HypF in the conversion of carbamoyl phosphate to the CN ligand.
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PMID:HypF, a carbamoyl phosphate-converting enzyme involved in [NiFe] hydrogenase maturation. 1237 78

Creation of the Department of Biochemistry of Microorganisms at the Institute of Microbiology and Virology of the Academy of Sciences of Ukrainian SSR in the 30's of the last century was determined by a necessity of profound investigation of vital activity biochemism of microorganisms from various systematic groups which were studied in microbiological department of the Institute. Such complexity can explain certain diversity of the Department research at initial stages of its existence. The research of saccharose transformation into dextran Leuconostoc mesenteroides, when production solutions become slingy at sugar-refinaries, was one of the first most significant works of the Department. The enzyme saccharose-glycosyl-transferase performing this process was described for the first time. A cycle of works on the study of enzymes splitting lactose in milk under the effect of Streptococcus lactis has been carried out. Complex investigation of a number of proteins, polysaccharides, enzymes in enterobacteria has shown that the blocking of the enzyme aldolase is one of the reasons of alkali formation. A method has been developed for isolation of arenarin, antibiotic of plant origin, from sandy everlasting, the nature of its acting basis has been established. Nufarin, an active antibiotic, was isolated from the roots of white water lily when studying nitrogen fixation processes, special attention was given to interaction of hydrogenase and enzymes, taking part in nitrogen fixation, to the effect of ATP on these processes, ways of its synthesis, localization of ATPase in the cell membranes. Works on the study of lypopolysaccharides and polysaccharides of Gram-negative enterobacteria, bacteria of Pseudomonas genus were started with the purpose to use the obtained data to specify systematic propositions of the investigated microorganisms. Further on these works became the basis of thematic department. There are numerous reviews dedicated to their development.
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PMID:[Department of Biochemistry of Microorganisms--start of the path (1951-1973)]. 1277 2

The number of accessible SH-groups was determined in membrane vesicles prepared from Escherichia coli growing in fermentation conditions at slightly alkaline pH on glucose with or without added formate. Addition of ATP or formate to the vesicles caused a approximately 1.4-fold increase in the number of accessible SH-groups. The increase was inhibited by treatment with N-ethylmaleimide or the presence of the F(0)F(1)-ATPase inhibitors N,N(')-dicyclohexylcarbodiimide or sodium azide. The increase in accessible SH-groups was also absent in strains with the ATP synthase operon deleted or with the single F(0) domain cysteine Cysb21 changed to Ala. Using hyc and hyf mutants, it was shown that the increase was also largely dependent on hydrogenase 4 or hydrogenase 3, main components of formate hydrogen lyase, when bacteria were grown in the absence or presence of added formate. These results suggest a relationship between the F(0)F(1)-ATP synthase and hydrogenase 4 or hydrogenase 3 under fermentation conditions.
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PMID:The number of accessible SH-groups in Escherichia coli membrane vesicles is increased by ATP or by formate. 1291

Available data suggest that unusual organelles called hydrogenosomes, that make ATP and hydrogen, and which are found in diverse anaerobic eukaryotes, were once mitochondria. The evolutionary origins of the enzymes used to make hydrogen, pyruvate:ferredoxin oxidoreductase (PFO) and hydrogenase, are unresolved, but it seems likely that both were present at an early stage of eukaryotic evolution. Once thought to be restricted to a few unusual anaerobes, these proteins are found in diverse eukaryotic cells, including our own, where they are targeted to different cell compartments. Organelles related to mitochondria and hydrogenosomes have now been found in species of anaerobic and parasitic protozoa that were previously thought to have separated from other eukaryotes before the mitochondrial endosymbiosis. Thus it is possible that all eukaryotes may eventually be shown to contain an organelle of mitochondrial ancestry, bearing testimony to the important role that the mitochondrial endosymbiosis has played in eukaryotic evolution. It remains to be seen if members of this family of organelles share a common function essential to the eukaryotic cell, that provides the underlying selection pressure for organelle retention under different living conditions.
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PMID:Hydrogenosomes, mitochondria and early eukaryotic evolution. 1458 89

Anaerobic chytridiomycete fungi possess hydrogenosomes, which generate hydrogen and ATP, but also acetate and formate as end-products of a prokaryotic-type mixed-acid fermentation. Notably, the anaerobic chytrids Piromyces and Neocallimastix use pyruvate:formate lyase (PFL) for the catabolism of pyruvate, which is in marked contrast to the hydrogenosomal metabolism of the anaerobic parabasalian flagellates Trichomonas vaginalis and Tritrichomonas foetus, because these organisms decarboxylate pyruvate with the aid of pyruvate:ferredoxin oxidoreductase (PFO). Here, we show that the chytrids Piromyces sp. E2 and Neocallimastix sp. L2 also possess an alcohol dehydrogenase E (ADHE) that makes them unique among hydrogenosome-bearing anaerobes. We demonstrate that Piromyces sp. E2 routes the final steps of its carbohydrate catabolism via PFL and ADHE: in axenic culture under standard conditions and in the presence of 0.3% fructose, 35% of the carbohydrates were degraded in the cytosol to the end-products ethanol, formate, lactate and succinate, whereas 65% were degraded via the hydrogenosomes to acetate and formate. These observations require a refinement of the previously published metabolic schemes. In particular, the importance of the hydrogenase in this type of hydrogenosome has to be revisited.
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PMID:The anaerobic chytridiomycete fungus Piromyces sp. E2 produces ethanol via pyruvate:formate lyase and an alcohol dehydrogenase E. 1498 32

Hydrogen oxidation and electron transport were studied in the chlorobenzene-utilizing anaerobe Dehalococcoides sp. strain CBDB1. While Cu(2+) and Hg(2+) ions irreversibly inhibited hydrogenase activity in intact cells, Ni(2+) ions inhibited reversibly. About 80% of the initial hydrogenase activity was inactivated within 30 s when the cells were exposed to air. In contrast, hydrogenase was active at a redox potential of +10 mV when this redox potential was established anoxically with a redox indicator. Viologen dyes served both as electron acceptor for hydrogenase and electron donor for the dehalogenase. A menaquinone analogue, 2,3-dimethyl 1,4-naphthoquinone, served neither as electron acceptor for the hydrogenase nor as electron donor for the dehalogenase. In addition, the menaquinone antagonist 2-n-heptyl-4-hydroxyquinoline-N-oxide had no effect on dechlorination catalyzed by cell suspensions or isolated membranes with hydrogen as electron donor, lending further support to the notion that menaquinone is not involved in electron transport. The ionophores tetrachlorosalicylanilide and carbonylcyanide m-chlorophenylhydrazone did not inhibit dechlorination by cell suspensions, indicating that strain CBDB1 does not require reverse electron transport. The ATP-synthase inhibitor N,N'-dicyclohexylcarbodiimide inhibited the dechlorination reaction with cell suspensions; however, the latter effect was partially relieved by the addition of tetrachlorosalicylanilide. 1,2,3,4-tetrachlorobenzene strongly inhibited dechlorination of other chlorobenzenes by cell suspensions with hydrogen as electron donor, but it did not interfere with either hydrogenase or dehalogenase activity.
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PMID:Studies on hydrogenase activity and chlorobenzene respiration in Dehalococcoides sp. strain CBDB1. 1549 Jan 22


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