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  • 1
    Digitale Medien
    Digitale Medien
    Cyclic 2,3-diphosphoglycerate metabolism in Methanobacterium thermoautotrophicum (strain ΔH): characterization of the synthetase reaction (1994)
    Springer
    Archives of microbiology 162 (1994), S. 193-198 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Methanobacterium thermoautotrophicum ; Cyclic 2,3-diphosphoglycerate ; 2,3-Diphosphoglycerate ; Cyclic 2,3-diphosphoglycerate synthetase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The levels of cyclic 2,3-diphosphoglycerate (cDPG) in methanogenic bacteria are governed by the antagonistic activities of cDPG synthetase and cDPG hydrolase. In this paper we focus on the synthetase from Methanobacterium thermoautotrophicum. The cytoplasmic 150 kDa enzyme catalyzed cDPG synthesis from 2,3-diphosphoglycerate (apparent Km=21 mM), Mg2+ (Km=3.1 mM) and ATP (Km=1–2 mM). In batch-fed cultures, the enzyme was constitutively present (6–6.5 nmol per min per mg protein) during the different growth phases. In continuous cultures, activity decreased in response to phosphate limitation. The synthetase reaction proceeded with maximal rate at pH 6 and at 65° C and was specifically dependent on high (〉0.3M) K+ concentrations. The reaction conditions remarkably contrasted to those of cDPG degradation catalyzed by the previously described membrane-bound cDPG hydrolase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314474
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  • 2
    Digitale Medien
    Digitale Medien
    Stimulation of the methyltetrahydromethanopterin: coenzyme M methyltransferase reaction in cell-free extracts of Methanobacterium thermoautotrophicum by the heterodisulfide of coenzyme M and 7-mercaptoheptanoylthreonine phosphate (1990)
    Springer
    Archives of microbiology 154 (1990), S. 156-161 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Methanobacterium thermoautotrophicum ; Coenzyme M ; 7-Mercaptoheptanoylthreonine phosphate ; 5-Methyltetrahydromethanopterin: coenzyme M methyltransferase ; Corrinoid enzyme ; Reductive activation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The conversion of formaldehyde to methylcoenzyme M in cell-free extracts of Methanobacterium thermoautotrophicum was stimulated up to 10-fold by catalytic amounts of the heterodisulfide (CoM-S-S-HTP) of coenzyme M and 7-mercaptoheptanoylthreonine phosphate. The stimulation required the additional presence of ATP, also in catalytic concentrations. ATP and CoM-S-S-HTP were mutually stimulatory on the methylcoenzyme M formation and it was concluded that the compounds were both involved in the reductive activation of the methyltetrahydromethanopterin: coenzyme M methyltransferase. Micromolar concentrations of benzyl viologen or cyanocobalamin inhibited the formaldehyde conversion; these compounds, however, strongly stimulated the reduction of CoM-S-S-HTP. The results described here closely resemble observations made on the activation and reduction of CO2 to formylmethanofuran indicating that this step and the reductive activation of the methyltransferase are controlled by some common mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00423326
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  • 3
    Digitale Medien
    Digitale Medien
    Reductive activation of the methyl-tetrahydromethanopterin: coenzyme M methyltransferase from Methanobacterium thermoautotrophicum strain ΔH (1988)
    Springer
    Archives of microbiology 150 (1988), S. 405-412 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Methanobacterium thermoautotrophicum ; Activation ; Corrinoid enzyme ; Methyltransferase ; Methanopterin ; Coenzyme M
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The enzymatic conversion of formaldehyde to CH3S-CoM in crude extracts of Methanobacterium thermoautotrophicum was used as a means to investigate the methyl-tetrahydromethanopterin: HS-CoM methyltransferase reaction. All components necessary for formaldehyde conversion were shown to be present in a soluble protein fraction. This soluble cell fraction still contained a major amount of corrinoids. Apart from tetrahydromethanopterin no other soluble cofactors were required for formaldehyde conversion. The dependence of the system on catalytic amounts of ATP was shown to be specific. Several nucleoside triphosphates or ADP were unable to substitute for ATP. Remarkably, various strong reducing systems, especially titanium(III)citrate could replace ATP to a large extent. The ATP-dependent formaldehyde conversion to CH3S-CoM was inhibited in the presence of nitrous oxide, detergents or 2′,3′-dialdehyde-ATP. The results support a role for a corrinoid protein in the methyl-tetrahydromethanopterin: HS-CoM methyltransferase reaction at which ATP is involved in the activation of this protein, probably in the conversion of inactive B12a or B12r to active B12s.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00408315
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