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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Function of coenzyme F420-dependent NADP reductase in methanogenic archaea containing an NADP-dependent alcohol dehydrogenase (1997)
    Springer
    Archives of microbiology 168 (1997), S. 396-402 
    Details
    ISSN: 1432-072X
    Keywords: Key words Coenzyme F420 ; F420-dependent NADP ; reductase ; F420-dependent N5 ; N10-methylenetetrahydromethanopterin dehydrogenase ; F420-dependent N5 ;  N10-methylenetetrahydromethanopterin reductase ; Methanogenic archaea ; Methanogenium organophilum ; Methanobacterium palustre ; Methanogenium liminatans ; Methanoculleus ; thermophilicus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methanogenic archaea growing on ethanol or isopropanol as the electron donor for CO2 reduction to CH4 contain either an NADP-dependent or a coenzyme F420-dependent alcohol dehydrogenase. We report here that in both groups of methanogens, the N 5, N 10-methylenetetrahydromethanopterin dehydrogenase and the N 5, N 10-methylenetetrahydromethanopterin reductase, two enzymes involved in CO2 reduction to CH4, are specific for F420. This raised the question how F420H2 is regenerated in the methanogens with an NADP-dependent alcohol dehydrogenase. We found that these organisms contain catabolic activities of an enzyme catalyzing the reduction of F420 with NADPH. The F420-dependent NADP reductase from Methanogenium organophilum was purified and characterized. The N-terminal amino acid sequence showed 42% sequence identity to a putative gene product in Methanococcus jannaschii, the total genome of which has recently been sequenced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050514
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  • 3
    Electronic Resource
    Electronic Resource
    Activation and thermostabilization effects of cyclic 2,3-diphosphoglycerate on enzymes from the hyperthermophilic Methanopyrus kandleri (1998)
    Springer
    Archives of microbiology 170 (1998), S. 469-472 
    Details
    ISSN: 1432-072X
    Keywords: Key words Methanogenic archaea ; Formyltransferase ; Cyclohydrolase ; N5 ; N10-Methenyltetrahydromethanopterin ; Formylmethanofuran ; Halophilic enzymes ; Thermophilic enzymes ; 2-Phosphoglycerate kinase ; Cyclic diphosphoglycerate ; synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Enzymes involved in methane formation from carbon dioxide and dihydrogen in Methanopyrus kandleri require high concentrations (〉 1 M) of lyotropic salts such as K2HPO4/KH2PO4 or (NH4)2SO4 for activity and for thermostability. The requirement correlates with high intracellular concentrations of cyclic 2,3-diphosphoglycerate (cDPG; ≈ 1 M) in this hyperthermophilic organism. We report here on the effects of potassium cDPG on the activity and thermostability of the two methanogenic enzymes cyclohydrolase and formyltransferase and show that at cDPG concentrations prevailing in the cells the investigated enzymes are highly active and completely thermostable. At molar concentrations also the potassium salts of phosphate and of 2,3-bisphosphoglycerate, the biosynthetic precursor of cDPG, were found to confer activity and thermostability to the enzymes. Thermodynamic arguments are discussed as to why cDPG, rather than these salts, is present in high concentrations in the cells of Mp. kandleri.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050669
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  • 4
    Electronic Resource
    Electronic Resource
    Coenzyme F420 dependent N5, N10-methylenetetrahydromethanopterin dehydrogenase in methanol grown Methanosarcina barkeri (1991)
    Springer
    Archives of microbiology 155 (1991), S. 483-490 
    Details
    ISSN: 1432-072X
    Keywords: Methanosarcina barkeri ; Methanogenesis ; Tetrahydromethanopterin ; Coenzyme F420 ; Affinity chromatography ; Blue Sepharose CL-6B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dehydrogenation of N 5,N 10-methylenetetrahydromethanopterin (CH2=H4MPT) to N 5,N 10-methenyltetrahydromethanopterin (CH≡H4MPT+) is an intermediate step in the oxidation of methanol to CO2 in Methanosarcina barkeri. The reaction is catalyzed by CH2=H4MPT dehydrogenase, which was found to be specific for coenzyme F420 as electron acceptor; neither NAD, NADP nor viologen dyes could substitute for the 5-deazaflavin. The dehydrogenase was anaerobically purified almost 90-fold to apparent homogeneity in a 32% yield by anion exchange chromatography on DEAE Sepharose and Mono Q HR, and by affinity chromatography on Blue Sepharose. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed only one protein band with an apparent mass of 31 kDa. The apparent molecular mass of the native enzyme determined by polyacrylamide gradient gel electrophoresis was 240 kDa. The ultraviolet/visible spectrum of the purified enzyme was almost identical to that of albumin suggesting the absence of a chromophoric prosthetic group. Reciprocal plots of the enzyme activity versus the substrate concentrations were linear: the apparent K m for CH2=H4MPT and for coenzyme F420 were found to be 6 μM and 25 μM, respectively. Vmax was 4,000 μmol min-1·mg-1 protein (kcat=2,066 s-1) at pH 6 (the pH optimum) and 37°C. The Arrhenius activation energy was 40 kJ/mol. The N-terminal amino acid sequence was found to be 50% identical with that of the F420-dependent CH2=H4MPT dehydrogenase isolated from H2/CO2 grown Methanobacterium thermoautotrophicum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00244966
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  • 5
    Electronic Resource
    Electronic Resource
    N 5,N 10-Methylenetetrahydromethanopterin reductase (coenzyme F420-dependent) and formylmethanofuran dehydrogenase from the hyperthermophile Archaeoglobus fulgidus (1991)
    Springer
    Archives of microbiology 156 (1991), S. 427-434 
    Details
    ISSN: 1432-072X
    Keywords: Sulfate-reducing archaebacteria ; Hyperthermophilic bacteria ; Archaeglobus fulgidus ; Tetrahydromethanopterin ; Methanofuran ; Coenzyme F420 ; Thermostable enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methylene-H4MPT reductase was found to be present in Archaeoglobus fulgidus in a specific activity of 1 U/mg. The reductase was purified 410-fold. The native enzyme showed an apparent molecular mass of approximately 200 kDa. Sodium dodecylsulfate/polyacrylamide gel electrophoresis revealed the presence of only 1 polypeptide of apparent molecular mass 35 kDa. The ultraviolet/visible spectrum of the reductase was almost identical to that of albumin indicating the absence of a chromophoric prosthetic group. The reductase was dependent on reduced coenzyme F420 as electron donor. Neither NADH, NADPH, nor reduced viologen dyes could substitute for the reduced deazaflavin. From reciprocal plots, which showed an intersecting patter, a K m for methylene-H4MPT of 16 μM, a K m for F420H2 of 4 μM, and a V max of 450 U/mg (Kcat=265 s-1) were obtained. The enzyme was found to be rapidly inactivated when incubated at 80°C in 100 mM Tris/HCl pH 7. The rate of inactivation, however, decreased to essentially zero in the presence of either F420 (0.2 mM), methylene-H4MPT (0.2 mM), albumin (1 mg/ml), or KCl (0.5 M). The N-terminal amino acid sequence was determined and found to be similar to that of methylene-H4MPT reductase (F420-dependent) from the methanogens Methanobacterium thermoautotrophicum, Methanosarcina barkeri, and Methanopyrus kandleri. The purification and some properties of formylmethanofuran dehydrogenase from A. fulgidus are also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248722
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  • 6
    Electronic Resource
    Electronic Resource
    Different mechanisms of acetate activation in Desulfurella acetivorans and Desulfuromonas acetoxidans (1990)
    Springer
    Archives of microbiology 154 (1990), S. 274-279 
    Details
    ISSN: 1432-072X
    Keywords: Desulfurella ; Desulfuromonas ; Sulfur reduction ; Acetate oxidation ; Citric acid cycle ; Menaquinone ; Cytochromes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Desulfurella acetivorans and Desulfuromonas acetoxidans are both acetate oxidizing sulfur reducing eubacteria. The two organisms differ in G+C content of DNA (31.4% versus 50–52%) and in growth temperature optimum (55°C versus 30°C) and in that D. acetivorans does not contain cytochromes. Both organisms are shown to be similar in that they metabolize acetate via the citric acid cycle rather than via the carbon monoxide dehydrogenase pathway. They were found to differ, however, in the mechanism of acetate activation and of succinate formation. In D. acetoxidans acetyl-CoA and succinate are formed from acetate and succinyl-CoA involving only one enzyme, succinyl-CoA: acetate CoA-transferase. In D. acetivorans acetyl-CoA is generated from acetate via acetyl phosphate involving acetate kinase and phosphate acetyltransferase; succinate is formed from succinyl-CoA via succinyl-CoA synthetase. Both sulfur reducers were found to contain menaquinone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248967
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  • 7
    Electronic Resource
    Electronic Resource
    N 5,N 10-Methenyltetrahydromethanopterin cyclohydrolase from the extremely thermophilic sulfate reducing Archaeoglobus fulgidus: comparison of its properties with those of the cyclohydrolase from the extremely thermophilic Methanopyrus kandleri (1993)
    Springer
    Archives of microbiology 159 (1993), S. 213-219 
    Details
    ISSN: 1432-072X
    Keywords: Archaea ; Methanogenic bacteria ; Hyperthermophiles ; Sulfate reducers ; Methanobacterium thermoautotrophicum ; Methanosarcina barkeri ; Tetrahydromethanopterin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Archaeoglobus fulgidus and Methanopyrus kandleri are both extremely thermophilic Archaea with a growth temperature optimum at 83°C and 98°C, respectively. Both Archaea contain an active N 5,N 10-methenyltetrahydromethanopterin cyclohydrolase. The enzyme from M. kandleri has recently been characterized. We describe here the purification and properties of the enzyme from A. fulgidus. The cyclohydrolase from A. fulgidus was purified 180-fold to apparent homogeneity and its properties were compared with those recently published for the cyclohydrolase from M. kandleri. The two cytoplasmic enzymes were found to have very similar molecular and catalytic properties. They differed, however, significantly with respect of the effect of K2HPO4 and of other salts on the activity and the stability. The cyclohydrolase from A. fulgidus required relatively high concentrations of K2HPO4 (1 M) for optimal thermostability at 90°C but did not require salts for activity. Vice versa, the enzyme from M. kandleri was dependent on high K2HPO4 concentrations (1.5 M) for optimal activity but not for thermostability. Thus the activity and structural stability of the two thermophilic enzymes depend in a completely different way on the concentration of inorganic salts. The molecular basis for these differences are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248474
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  • 8
    Electronic Resource
    Electronic Resource
    Formylmethanofuran: tetrahydromethanopterin formyltransferase and N 5,N 10-methylenetetrahydromethanopterin dehydrogenase from the sulfate-reducing Archaeoglobus fulgidus: similarities with the enzymes from methanogenic Archaea (1993)
    Springer
    Archives of microbiology 159 (1993), S. 225-232 
    Details
    ISSN: 1432-072X
    Keywords: Archaea ; Methanogens ; Sulfate reducers ; Tetrahydromethanopterin ; Methanofuran ; Coenzyme F420 ; C1-Enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sulfate-reducing Archaeoglobus fulgidus contains a number of enzymes previously thought to be unique for methanogenic Archaea. The purification and properties of two of these enzymes, of formylmethanofuran: tetrahydromethanopterin formyltransferase and of N 5,N 10-methylenetetrahydromethanopterin dehydrogenase (coenzyme F420 dependent) are described here. A comparison of the N-terminal amino acid sequences and of other molecular properties with those of the respective enzymes from three methanogenic Archaea revealed a high degree of similarity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248476
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  • 9
    Electronic Resource
    Electronic Resource
    Purification, properties and primary structure of H2-forming N5,N10-methylenetetrahydromethanopterin dehydrogenase from Methanococcus thermolithotrophicus (1996)
    Springer
    Archives of microbiology 165 (1996), S. 187-193 
    Details
    ISSN: 1432-072X
    Keywords: Key words Archaea ; Methanococcus ; Methane ; formation ; Hydrogenases ; H2-Forming dehydrogenase ; N5 ; N10-Methylenetetrahydromethanopterin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract H2-Forming N 5 ,N 10 -methylenetetrahydromethanopterin dehydrogenase (Hmd) is a novel type of hydrogenase found in methanogenic Achaea that contains neither nickel nor iron-sulfur clusters. The enzyme has previously been characterized from Methanobacterium thermoautotrophicum and from Methanopyrus kandleri. We report here on the purification and properties of the enzyme from Methanococcus thermolithotrophicus. The hmd gene was cloned and sequenced. The results indicate that the enzyme from Mc. thermolithotrophicus is functionally and structurally closely related to the H2-forming methylene tetrahydromethanopterin dehydrogenase from Mb. thermoautotrophicum and Mp. kandleri. From amino acid sequence comparisons of the three enzymes, a phylogenetic tree was deduced that shows branching orders similar to those derived from sequence comparisons of the 16S rRNA of the orders Methanococcales, Methanobacteriales, and Methanopyrales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01692860
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  • 10
    Electronic Resource
    Electronic Resource
    Function of H2-forming methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum in coenzyme F420 reduction with H2 (1998)
    Springer
    Archives of microbiology 169 (1998), S. 206-210 
    Details
    ISSN: 1432-072X
    Keywords: Key words Hydrogenases ; Coenzyme F420 ; N5 ;  N10-Methylenetetrahydromethanopterin ; Methanobacterium thermoautotrophicum ; Nickel-limited chemostat culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In most methanogenic archaea, two hydrogenase systems that can catalyze the reduction of coenzyme F420 (F420) with H2 are present: (1) the F420-reducing hydrogenase, which is a nickel iron-sulfur flavoprotein composed of three different subunits, and (2) the N 5, N10-methylenetetrahydromethanopterin dehydrogenase system, which is composed of H2-forming methylenetetrahydromethanopterin dehydrogenase and F420-dependent methylenetetrahydromethanopterin dehydrogenase, both metal-free proteins without an apparent prosthetic group. We report here that in nickel-limited chemostat cultures of Methanobacterium thermoautotrophicum, the specific activity of the F420-reducing Ni/Fe-hydrogenase was essentially zero, whereas that of the H2-forming methylenetetrahydromethanopterin dehydrogenase was six times higher, and that of the F420-dependent methylenetetrahydromethanopterin dehydrogenase was four times higher than in cells grown under non-nickel-limited conditions. This evidence supports the hypothesis that when M. thermoautotrophicum grows under conditions of nickel limitation, the reduction of F420 with H2 is catalyzed by the metal-free methylenetetrahydromethanopterin dehydrogenase system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050562
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