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  • 1
    ISSN: 1432-072X
    Keywords: Pyrococcus furiosus ; Archaea ; Hyperthermophiles ; Gluconeogenesis ; Embden-Meyerhof pathway ; Fructose-1,6-bisphosphate aldolase ; Fructose-1,6-bisphosphate phosphatase ; Glyceraldehyde-3-phosphate dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hyperthermophilic archaeon Pyrococcus furiosus was grown on pyruvate as carbon and energy source. The enzymes involved in gluconeogenesis were investigated. The following findings indicate that glucose-6-phosphate formation from pyruvate involves phosphoenolpyruvate synthetase, enzymes of the Embden-Meyerhof pathway and fructose-1,6-bisphosphate phosphatase. Cell extracts of pyruvate-grown P.furiosus contained the following enzyme activities: phosphoenolpyruvate synthetase (0.025 U/mg, 50 °C), enolase (0.9 U/mg, 80 °C), phosphoglycerate mutase (0.13 U/mg, 55 °C), phosphoglycerate kinase (0.01 U/mg, 50 °C), glyceraldehyde-3-phosphate dehydrogenase reducing either NADP+ or NAD+ (NADP+: 0.019 U/mg, NAD+: 0.009 U/mg; 50 °C), triosephosphate isomerase (1.4 U/mg, 50 °C), fructose-1,6-bisphosphate aldolase (0.0045 U/mg, 55 °C), fructose-1,6-bisphosphate phosphatase (0.026 U/mg, 75 °C), and glucose-6-phosphate isomerase (0.22 U/mg, 50 °C). Kinetic properties (V max values and apparent K m values) of the enzymes indicate that they operate in the direction of sugar synthesis. The specific enzyme activities of phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase (NADP+-reducing) and fructose-1,6-bisphosphate phosphatase in pyruvate-grown P. furiosus were by a factor of 3, 10 and 4, respectively, higher as compared to maltose-grown cells suggesting that these enzymes are induced under conditions of gluconeogenesis. Furthermore, cell extracts contained ferredoxin: NADP+ oxidoreductase (0.023 U/mg, 60 °C); phosphoenolpyruvate carboxylase (0.018 U/mg, 50 °C) acts as an anaplerotic enzyme. Thus, in P. furiosus sugar formation from pyruvate involves reactions of the Embden-Meyerhof pathway, whereas sugar degradation to pyruvate proceeds via a modified “non-phosphorylated” Entner-Doudoroff pathway.
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  • 2
    ISSN: 1432-072X
    Keywords: Thermoproteus tenax ; Pyrobaculum islandicum ; Hyperthermophiles ; Archaea ; Acetyl-CoA oxidation ; Citric acid cycle ; Sulfur respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The oxidation of organic compounds with elemental sulfur or thiosulfate as electron acceptor was studied in the anaerobic hyperthermophilic archaea Thermoproteus tenax and Pyrobaculum islandicum. T. tenax was grown on either glucose or casamino acids and sulfur; P. islandicum on peptone and either elemental sulfur or thiosulfate as electron acceptor. During exponential growth only CO2 and H2S rather than acetate, alanine, lactate, and succinate were detected as fermentation products of both organisms; the ratio of CO2/H2S formed was 1:2 with elemental sulfur and 1:1 with thiosulfate as electron acceptor. Cell extracts of T. tenax and P. islandicum contained all enzymes of the citric acid cycle in catabolic activities: citrate synthase, aconitase, isocitrate dehydrogenase (NADP+-reducing), oxoglutarate: benzylviologen oxidoreductase, succinyl-CoA synthetase, succinate dehydrogenase, fumarase and malate dehydrogenase (NAD+-reducing). Carbon monoxide dehydrogenase activity was not detected. We conclude that in T. tenax and P. islandicum organic compounds are completely oxidized to CO2 with sulfur or thiosulfate as electron acceptor and that acetyl-CoA oxidation to CO2 proceeds via the citric acid cycle.
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  • 3
    ISSN: 1432-072X
    Keywords: Pyrococcus furiosus ; Hyperthermophiles ; Sugar fermentation ; Non-phosphorylated Entner ; Doudoroff pathway ; 2-Keto-3-deoxy-gluconate aldolase ; Glyceraldehyde dehydrogenase ; 2-Phosphoglycerate-forming glycerate kinase ; ADP-depenent acetyl-CoA synthetase ; Substrate level phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hyperthermophilic anaerobe Pyrococcus furiosus was grown on maltose as energy and carbon source. During growth 1 mol maltose was fermented to 3–4 mol acetate, 6–7 mol H2 and 3–4 mol CO2. The presence of the following enzyme activities in cell extracts of maltose-grown P. furiosus indicate that the sugar is degraded to pyruvate and H2 by a modified “non-phosphorylated” Entner-Doudoroff-pathway (the values given in brackets are specific enzyme activities at 100 °C): Glucose: methyl viologen oxidoreductase (0.03 U/mg); 2-keto-3-deoxy-gluconate aldolase (0.03 U/mg); glyceraldehyde: benzyl viologen oxidoreductase (2.6 U/mg), glycerate kinase (2-phosphoglycerate forming) (0.48 U/mg), enolase (10.4 U/mg), pyruvate kinase (1.4 U/mg). Hexokinase, glucose-6-phosphate dehydrogenase, 2-keto-3-deoxy-6-phosphogluconate aldolase and phosphofructokinase could not be detected. Further conversion of pyruvate to acetate, CO2 and H2 involves pyruvate: ferredoxin oxidoreductase (0.4 U/mg; T=60°C with Clostridium pasteurianum ferredoxin as electron acceptor), hydrogen: methyl viologen ixodoreductase (3.4 U/mg) and ADP-dependent acetyl-CoA synthetase (1.9 U/mg). Phosphate acetyl transferase and acetate kinase could not be detected. The ADP-dependent acetyl-CoA synthetase catalyzes ATP synthesis via the mechanism of substrate level phosphorylation and apparently constitutes the only ATP conserving site during maltose catabolism in P. furiosus. This novel pathway of maltose fermentation to acetate, CO2 and H2 in the anaerobic archaeon P. furiosus may represent a phylogenetically ancient pathway of sugar fermentation.
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  • 4
    ISSN: 1432-072X
    Keywords: Thermotoga maritima ; Hyperthermophiles ; (Eu)Bacteria ; Glucose fermentation ; Acetate formation ; Embden-Meyerhof pathway ; Hexokinase ; Phosphofructokinase ; Acetake kinase ; Sulfur reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hyperthermophilic anaerobic eubacterium Thermotoga maritima was grown on glucose as carbon and energy source. During growth 1 mol glucose was fermented to 2 mol acetate, 2 mol CO2 and 4 mol H2. The molar growth yicld on glucose (Yglucose) was about 45 g cell dry mass/mol glucose. In the presence of elemental sulfur growing cultures of T. maritima converted 1 mol glucose to 2 mol acetate, 2 mol CO2 about 0.5 mol H2 and about 3.5 mol H2S. Yglucose was about 45 g/mol. Cell extracts contained all enzymes of the Embden-Meyerhof pathway: hexokinase (0.29 U/mg, 50°C), glucose-6-phosphate isomerase (0.56 U/mg, 50°C), phosphofructokinase (0.19 U/mg, 50° C), fructose-1,6-bisphosphate aldolase (0.033 U/mg, 50°C), triosephosphate isomerase (6.3 U/mg, 50°C), glyceraldehyde-3-phosphate dehydrogenase (NAD+ reducing: 0.63 U/mg, 50°C), phosphoglycerate kinase (3.7 U/mg, 50°C), phosphoglycerate mutase (0.4 U/mg, 50°C); enolase (4 U/mg, 80°C), pyruvate kinase (0.05 U/mg, 50°C). Furthermore, cell extracts contained pyruvate: ferredoxin oxidoreductasee (0.43 U/mg, 60°C); NADH: ferredoxin oxidoreductase (benzylviologen reduction: 0.46 U/mg, 80°C); hydrogenase (benzylviologen reduction: 15 U/mg, 80°C), phosphate acetyltransferase (0.13 U/mg, 80°C), acetate kinase (1.2 U/mg, 55°C), lactate dehydrogenase (0.16 U/mg, 80°C) and pyruvate carboxylase (0.02 U/mg, 50°C). The findings indicate that the hyperthermophilic eubacterium T. maritima ferments sugars (glucose) to acetate, CO2 and H2 involving the Embden-Meyerhof pathway, phosphate acetyltransferase and acetate kinase. Thus, the organism differs from the hyperthermophilic archaeon Pyrococcus furiosus which ferments sugars to acetate, CO2 and H2 involving a modified non-phosphorylated Entner-Doudoroff pathway and acetyl-CoA synthetase (ADP forming).
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  • 5
    ISSN: 1432-072X
    Keywords: Archaea ; Bacteria ; Hyperthermophiles ; Acetate formation ; Pyruvate: ferredoxin oxidoreductase ; Acetyl-CoA synthetase (ADP forming) ; Phosphate acetyltransferase ; Acetate kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The anaerobic hyperthermophilic archaea Desulfurococcus amylolyticus, Hyperthermus butylicus, Thermococcus celer, Pyrococcus woesei, the hyperthermophilic bacteria Thermotoga maritima and Clostridium thermohydrosulfuricum and the aerobic mesophilic archaeon Halobacterium saccharovorum were grown either on complex media, on sugars or on pyruvate as carbon and energy sources. During growth acetate was formed as fermentation product by all organisms. The enzymes involved in acetyl-CoA formation from pyruvate and in acetate formation from acetyl-CoA were investigated: 1. Cell extracts of all species, both archaea and bacteria, catalyzed the coenzyme A-dependent oxidative decarboxylation of pyruvate with viologen dyes or with Clostridium pasteurianum ferredoxin as electron acceptors indicating a pyruvate: ferredoxin oxidoreductase to be operative in acetyl-CoA formation from pyruvate. 2. Cell extracts of all archaeal species, both hyperthermophiles (D. amylolyticus, H. butylicus, T. celer, P. woesei) and the mesophile H. saccharovorum, contained an acetyl-CoA synthetase (ADP forming), which catalyzes both acetate formation from acetyl-CoA and ATP synthesis from ADP and phosphate (Pi): Acetyl-CoA+ADP+Pi⇌Acetate + ATP+CoA. Phosphate acetyltransferase and acetate kinase could not be detected. 3. Cell extracts of the hyperthermophilic (eu)bacteria T. maritima and C. thermohydrosulfuricum contained phosphate acetyltransferase and acetate kinase rather than acetyl-CoA synthetase (ADP forming). These data indicate that acetyl-CoA synthetase (ADP forming) represents a typical archaeal property rather than an enzyme specific for hyperthermophiles. It is proposed that in all acetate forming archaea the formation of acetate and of ATP from acetyl-CoA, ADP and Pi are catalyzed by acetyl-CoA synthetase (ADP forming), whereas in all acetate forming (eu)bacteria these reactions are catalyzed by two enzymes, phosphate acetyltransferase and acetate kinase.
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