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)

Recombinant cosmids from a gene library of the DNA from Hup+ Rhizobium japonicum 122DES previously have been shown to restore hydrogenase activity when transferred by conjugation into certain Hup- mutants of R. japonicum. We generated a restriction map covering 32.2 kilobases of this cosmid DNA. At least 25.3 kilobases of the cosmid pHU1 were shown to have the same arrangement as those in the genome of strain 122DES. Analysis of Tn5 insertions into the 122DES genome indicates that hup-specific sequences occur in a region spanning about 15 kilobases of insert DNA within pHU1. Introduction of pHU1 into five out of six R. japonicum Hup- mutants resulted in a Hup+ phenotype in some transconjugants. Three of the mutations appear to be in transcriptional units completely contained within pHU1, whereas the other two must be in genes that are at least partially contained within pHU1. pBR235 derivatives containing fragments of hup DNA can be transferred into the R. japonicum Hup- mutant PJ18nal if the derivatives contain a region of homology with the R. japonicum genome. The hup mutation in strain PJ18nal appears to be dominant. The hup genes in R. japonicum strain 122DES appear to be organized in at least two, and probably three, transcriptional units.
J Bacteriol 1984 Sep
PMID:Characterization of Rhizobium japonicum hydrogen uptake genes. 609 Mar 82

A c3 type cytochrome has been purified from the thermophilic, non-spore-forming, sulfate-reducing bacterium Thermodesulfobacterium commune. The purified protein was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gel filtration, and isoelectric focusing. A pI of 6.83 was observed. The molecular weight of the cytochrome was estimated to be ca. 13,000 from both gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The hemoprotein exhibited absorption maxima at 530, 408.5, and 351 nm in the oxidized form and 551.5 (alpha band), 522.5 (beta band), and 418.5 nm (gamma band) in the reduced form. The extinction coefficients of T. commune cytochrome c3 were 130,000, 74,120, and 975,000 M-1 cm-1 at 551.5, 522.5, and 418.5 nm, respectively. It contains four hemes per molecule, on the basis of both the iron estimation and the extinction coefficient value of its pyridine hemochrome. The amino acid composition showed the presence of eight cysteine residues involved in heme binding. T. commune cytochrome c3 had low threonine, serine, and glycine contents and high glutamic acid and hydrophobic residue contents. The electrochemical study of T. commune cytochrome c3 by cyclic voltammetry and differential pulse polarography has shown that the cytochrome system behaves like a reversible system. Four redox potential values at Eh1 = -0.140 +/- 0.010 V, Eh2 = Eh3 = Eh4 = -0.280 +/- 0.010 V have been determined. T. commune cytochrome c3, which acts as the physiological electron carrier of hydrogenase, is similar in most respects to the multiheme low-potential cytochrome c3 which is characteristic of the genus Desulfovibrio.
J Bacteriol 1984 Sep
PMID:Characterization of cytochrome c3 from the thermophilic sulfate reducer Thermodesulfobacterium commune. 609 Mar 84

Extensive information is available on the enzymology of respiratory sulphate reduction and the structure of electron transfer proteins isolated from the sulphate-reducing bacteria; however, it has not yet been possible to delineate satisfactorily the function of these electron transfer proteins in terms of the enzymes involved in respiratory sulphate reduction. New information about differences in pyrophosphate metabolism by Desulfovibrio and Desulfotomaculum, cellular localizations of electron transfer proteins and enzymes, and the concepts of vectorial electron transfer plus hydrogen cycling suggest that previous data on the function of electron transfer proteins must be re-evaluated and new experimental approaches designed before the problem is resolved. New information on the enzymology of lactate dehydrogenase, pyruvate dehydrogenase, adenylyl sulphate reductase, bisulphite reductase and hydrogenase is presented and discussed in the context of enzyme localization and specifically for electron transfer proteins. The function of cytochrome c3 (Mr = 13000) in the mechanism of the periplasmic hydrogenase and the role of the new [3Fe-3S] non-haem iron centres in electron transfer is emphasized.
Philos Trans R Soc Lond B Biol Sci 1982 Sep 13
PMID:Biochemistry of dissimilatory sulphate reduction. 612 35

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)
Biochim Biophys Acta 1984 Sep 06
PMID:The bioenergetics of methanogenesis. 623 47

Production of H2 by Azospirillum brasilense under N2-fixing conditions was studied in continuous and batch cultures. Net H2 production was consistently observed only when the gas phase contained CO. Nitrogenase activity (C2H2 reduction) and H2 evolution (in the presence of 5% CO) showed a similar response to O2 and were highest at 0.75% dissolved O2. Uptake hydrogenase activity, ranging from 0.3 to 2.5 mumol H2/mg protein per hour was observed in batch cultures under N2. Such rates were more than sufficient to recycle nitrogenase-produced H2. Tritium-exchange assay showed that H2 uptake was higher under Ar than under N2. Uptake hydrogenase was strongly inhibited by CO and C2H2. Cyclic GMP inhibited both nitrogenase and uptake hydrogenase activities.
Can J Microbiol 1980 Sep
PMID:Hydrogen metabolism of Azospirillum brasilense in nitrogen-free medium. 625 62

The uptake hydrogenase of chemolithotrophically grown Rhizobium japonicum was purified to apparent homogeneity with a final specific activity of 69 mumol of H2 oxidized per min per mg of protein. The procedure included Triton extraction of broken membranes and DEAE-cellulose and Sephacryl S-200 chromatographies. The purified protein contained two polypeptides separable only by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. They comigrated on native polyacrylamide gels and sucrose density gradients. The molecular weights were ca. 60,000 and 30,000. Densitometric scans of the sodium dodecyl sulfate gels indicated a molar ratio of 1.03 +/- 0.03. Antiserum was developed against the 60-kilodalton polypeptide for use in hydrogenase detection by an enzyme-linked immunosorbent assay. The antiserum did not cross-react with the 30-kilodalton polypeptide. Native gel electrophoresis of Triton-extracted cells grown in the presence of 63Ni showed comigration of the hydrogenase and radioactive Ni.
J Bacteriol 1984 Sep
PMID:Some properties of the nickel-containing hydrogenase of chemolithotrophically grown Rhizobium japonicum. 638 83

Desulfovibrio vulgaris Madison and Thermodesulfobacterium commune contained functionally distinct hydrogenase activities, one which exchanged 3H2 into 3H2O and was inhibited by carbon monoxide and a second activity which produced H2 in the presence of CO. Cell suspensions of D. vulgaris used either lactate, pyruvate, or CO as the electron donor for H2 production in the absence of sulfate. Both sulfidogenic species produced and consumed hydrogen as a trace gas during growth on lactate or pyruvate as electron donors and on thiosulfate or sulfate as electron acceptors. Higher initial levels of hydrogen were detected during growth on lactate-sulfate than on pyruvate-sulfate. D. vulgaris but not T. commune also produced and then consumed CO during growth on organic electron donors and sulfate or thiosulfate. High partial pressures of exogenous H2 inhibited growth and substrate consumption when D. vulgaris was cultured on pyruvate alone but not when it was metabolizing pyruvate plus sulfate or lactate plus sulfate. The data are discussed in relation to supporting two different models for the physiological function of H2 metabolism during growth of sulfidogenic bacteria on organic electron donors plus sulfate. A trace H2 transformation model is proposed for control of redox processes during growth on either pyruvate or lactate plus sulfate, and an obligate H2 cycling model is proposed for chemiosmotic energy coupling during growth on CO plus sulfate.
J Bacteriol 1984 Sep
PMID:Physiological function of hydrogen metabolism during growth of sulfidogenic bacteria on organic substrates. 648 May 53

Work with single muscle fibers from the barnacle Balanus nubilus has revealed that these fibers can be rendered sensitive to external application of aldosterone by preexposing the barnacle in vivo to the steroid for 16 h. Experiments investigating the dose-response relationship, glucocorticoid sensitivity of the preparation, and the role of the mitochondria in the aldosterone response in this preparation are presented. It is demonstrated that saturation kinetics may be seen in the dose-response curve if care is taken to isolate only fibers from animals that are in midmolt cycle. Data is presented that demonstrated a specific mineralocorticoid response to aldosterone in this preparation rather than a combined mineralocorticoid-glucocorticoid response, as has been demonstrated in other preparations. Experiments investigating the role of the mitochondrial inhibitors and substrates suggest that aldosterone modulates Na efflux in barnacle muscle fibers by altering mitochondrial function, presumably at the level of succinic hydrogenase.
Am J Physiol 1983 Sep
PMID:Further observations of aldosterone response in barnacle muscle fibers. 661 62

The sulfur atoms of the two [4Fe-4S] clusters present in the ferredoxin from Clostridium pasteurianum have been replaced by selenium. The substitution is readily carried out by incubating the apoferredoxin with excess amounts of Fe3+, selenite, and dithiothreitol under anaerobic conditions. The UV-visible absorption spectrum of the Se-substituted ferredoxin, the core extrusion of its active sites, and analyses of its iron and selenium contents show that it contains two [4Fe-4Se] clusters. The Se-substituted ferredoxin is considerably less resistant to oxygen or to acidic and alkaline pH than the native ferredoxin: the half-lives of the former are 20-500 times shorter than those of the latter. The native ferredoxin and the Se-substituted ferredoxin display similar kinetic properties when used as electron donors to the hydrogenase from C. pasteurianum. It is of note, however, that the Km and Vmax values are lower for the 2[4Fe-4Se] ferredoxin than for the 2[4Fe-4S] ferredoxin. Reductive and oxidative titrations with dithionite and with thionine, respectively, show that both ferredoxins are two-electron carriers. The redox potentials of the ferredoxins have been measured by equilibrating them with the H2/H+ couple via hydrogenase: values of -423 and -417 mV have been found for the 2[4Fe-4S] ferredoxin and 2[4Fe-4Se] ferredoxin, respectively. Ferredoxins containing both chalcogenides in their [4Fe-4X] (X = S, Se) clusters have been prepared by reconstitution reactions involving mixtures of sulfide and selenide: the latter experiments show that sulfide and selenide are equally reactive in the incorporation of [4Fe-4X] (X = S, Se) sites into ferredoxin. The present report, together with former studies, establishes the general feasibility of the Se/S substitution in [2Fe-2S] and in [4Fe-4S] clusters of proteins and of synthetic analogues.
Biochemistry 1982 Sep 14
PMID:Characterization of the selenium-substituted 2 [4Fe-4Se] ferredoxin from Clostridium pasteurianum. 675 26

Previous studies have established that the effects of estradiol (E2) on hepatic steroid and drug metabolism are demonstrable only in the presence of the pituitary gland. Studies were carried out to test the hypothesis that GH is the pituitary feminizing factor mediating the actions of E2 on hepatic metabolism. E2 and GH administered to castrated male rats had similar effects on hepatic enzymes, decreasing the oxidataive metabolism of drugs [ethylmorphine demethylation, aniline, hydroxylation, and benzo(a)pyrene hydroxylation) and increasing steroid (corticosterone) delta 4-hydrogenase activity. None of these effects of E2 or GH could be demonstrated in hypophysectomized (hypox) rats. However, GH administration to T4- or ACTH-treated hypox rats resulted in some of the changes in drug and steroid metabolism seen in animals with intact pituitary glands. The actions of GH on hepatic microsomal enzymes were fully demonstrable in hypox rats receiving both T4 and ACTH. E2 had no effects in T4 plus ACTH-treated hypox rats. These and prior observations are consistent with the hypothesis that GH mediates the actions of E2 on hepatic microsomal drug- and steroid-metabolizing enzymes. The data also indicates that the cations of GH on hepatic metabolism are dependent upon the interactions with still other endocrine factors.
Endocrinology 1980 Sep
PMID:Is growth hormone the pituitary feminizing factor mediating the actions of estradiol on hepatic drug and steroid metabolism? 677 28


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