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  • 1
    Electronic Resource
    Electronic Resource
    Acetate oxidation to CO2 via a citric acid cycle involving an ATP-citrate lyase: a mechanism for the synthesis of ATP via substrate level phosphorylation in Desulfobacter postgatei growing on acetate and sulfate (1987)
    Springer
    Archives of microbiology 148 (1987), S. 202-207 
    Details
    ISSN: 1432-072X
    Keywords: ATP-citrate lyase ; Citric acid cycle ; Acetate oxidation ; ATP synthesis via substrate level phosphorylation ; Sulfate-reducing bacteria ; Desulfobacter postgatei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Desulfobacter postgatei is an acetate-oxidizing, sulfate-reducing bacterium that metabolizes acetate via the citric acid cycle. The organism has been reported to contain a si-citrate synthase (EC 4.1.3.7) which is activated by AMP and inorganic phosphate. It is show now, that the enzyme mediating citrate formation is an ATP-citrate lyase (EC 4.1.3.8) rather than a citrate synthase. Cell extracts (160,000xg supernatant) catalyzed the conversion of oxaloacetate (apparent K m=0.2 mM), acetyl-CoA (app. K m=0.1 mM), ADP (app. K m=0.06 mM) and phosphate (app. K m=0.7 mM) to citrate, CoA and ATP with a specific activity of 0.3 μmol·min-1·mg-1 protein. Per mol citrate formed 1 mol of ATP was generated. Cleavage of citrate (app. K m=0.05 mM; V max=1.2 μmol · min-1 · mg-1 protein) was dependent on ATP (app. K m=0.4 mM) and CoA (app. K m=0.05 mM) and yielded oxaloacetate, acetyl-CoA, ADP, and phosphate as products in a stoichiometry of citrate:CoA:oxaloacetate:ADP=1:1:1:1. The use of an ATP-citrate lyase in the citric acid cycle enables D. postgatei to couple the oxidation of acetate to 2 CO2 with the net synthesis of ATP via substrate level phosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414812
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  • 2
    Electronic Resource
    Electronic Resource
    Membrane-bound NADPH dehydrogenase- and ferredoxin: NADP oxidoreductase activity involved in electron transport during acetate oxidation to CO2 in Desulfobacter postgatei (1988)
    Springer
    Archives of microbiology 150 (1988), S. 145-154 
    Details
    ISSN: 1432-072X
    Keywords: Acetate oxidation ; Citric acid cycle ; ATPase ; Energy conservation ; Electron transport ; Ferredoxin: NADP oxidoreductase ; NADPH dehydrogenase ; Succinate dehydrogenase ; Malate dehydrogenase ; Heptylhydroxyquinoline-N-oxide ; Sulfate-reducing bacteria ; Desulfobacter postgatei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Desulfobacter postgatei grows on acetate and sulfate as energy source. The oxidation of acetate to 2 CO2 proceeds via the citric acid cycle involving membrane-bound succinate dehydrogenase and membrane-bound malate dehydrogenase. We report here that the organism contains membrane-bound NADPH dehydrogenase and ferredoxin: NADP oxidoreductase for the reoxidation of NADPH and reduced ferredoxin generated during isocitrate- and 2-oxoglutarate oxidation, respectively. The presence of proton translocating ATPase activity is also described. NADPH dehydrogenase and succinate dehydrogenase were found to be electrically connected within the membrane and electron transfer between these two enzymes was shown to be coupled with proton translocation. The membrane fraction catalyzed the oxidation of NADPH with fumarate and the reduction of NADP with succinate. NADPH oxidation with fumarate was stimulated by protonophores and inhibited by the proton translocating ATPase inhibitor dicyclohexylcarbodiimide (DCCD) and by heptylhydroxyquinoline-N-oxide (HQNO); inhibition by DCCD was relieved by protonophores. NADP reduction with succinate was dependent on ATP and inhibited by protonophores, DCCD, and HQNO. The membrane fraction also mediated the oxidation of NADPH with the water soluble menaquinone analogue dimethylnaphthoquinone (DMN) and the reduction of fumarate with DMNH2. Only the former reaction was stimulated by protonophores and only the latter reaction was inhibited by HQNO. This suggests that the NADPH dehydrogenase reaction is the site of energy conservation and the succinate dehydrogenase is the site of HQNO inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425154
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  • 3
    Electronic Resource
    Electronic Resource
    Function of methanofuran, tetrahydromethanopterin, and coenzyme F420 in Archaeoglobus fulgidus (1989)
    Springer
    Archives of microbiology 152 (1989), S. 362-368 
    Details
    ISSN: 1432-072X
    Keywords: Archaebacteria ; Thermophiles ; Archaeoglobus ; Sulfate-reducing bacteria ; F420 ; Methanofuran ; Tetrahydromethanopterin ; Carbon monoxide dehydrogenase ; Acetyl-CoA/carbon monoxide dehydrogenase pathway ; Citric acid cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Archaeoglobus fulgidus is an extremely thermophilic archaebacterium that can grow at the expense of lactate oxidation with sulfate to CO2 and H2S. The organism contains coenzyme F420, tetrahydromethanopterin, and methanofuran which are coenzymes previously thought to be unique for methanogenic bacteria. We report here that the bacterium contains methylenetetrahydromethanopterin: F420 oxidoreductase (20 U/mg), methenyltetrahydromethanopterin cyclohydrolase (0.9 U/mg), formyltetrahydromethanopterin: methanofuran formyltransferase (4.4 U/mg), and formylmethanofuran: benzyl viologen oxidoreductase (35 mU/mg). Besides these enzymes carbon monoxide: methyl viologen oxidoreductase (5 U/mg), pyruvate: methyl viologen oxidoreductase (0.7 U/mg), and membranebound lactate: dimethylnaphthoquinone oxidoreductase (0.1 U/mg) were found. 2-Oxoglutarate dehydrogenase, which is a key enzyme of the citric acid cycle, was not detectable. From the enzyme outfit it is concluded that in A. fulgidus lactate is oxidized to CO2 via a modified acetyl-CoA/carbon monoxide dehydrogenase pathway involving C1-intermediates otherwise only used by methanogenic bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425174
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  • 4
    Electronic Resource
    Electronic Resource
    Anaerobic lactate oxidation to 3 CO2 by Archaeoglobus fulgidus via the carbon monoxide dehydrogenase pathway: demonstration of the acetyl-CoA carbon-carbon cleavage reaction in cell extracts (1990)
    Springer
    Archives of microbiology 153 (1990), S. 215-218 
    Details
    ISSN: 1432-072X
    Keywords: Archaeoglobus ; Archaebacteria ; Thermophiles ; Sulfate-reducing bacteria ; Lactate oxidation ; Carbon monoxide dehydrogenase ; Acetyl-CoA decarbonylation ; C1-pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell extracts of Archaeoglobus fulgidus were found to catalyze an isotope exchange between CO2 and the carbonyl group of acetyl-CoA. This observation and the presence of carbon monoxide: methyl viologen oxidoreductase activity strongly support the recent proposal that in A. fulgidus acetyl-CoA is degraded via a decarbonylation reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249070
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