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  • 1
    ISSN: 1432-072X
    Keywords: Methanobacterium thermoautotrophicum ; Cyclic 2,3-diphosphoglycerate ; 2,3-Diphosphoglycerate ; Cyclic 2,3-diphosphoglycerate synthetase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Methanobacterium thermoautotrophicum ; Cyclic 2,3-diphosphoglycerate ; 2,3-Diphosphoglycerate ; Cyclic 2,3-diphosphoglycerate hydrolase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyclic 2,3-diphosphoglycerate (cDPG) hydrolase activity was demonstrated in cofactor-free extract of Methanobacterium thermoautotrophicum (strain ΔH), but not in crude extract. Only after ultrafiltration or dialysis of crude extract cDPG hydrolase activity could be shown. cCPG hydrolysis was optimal at pH 6.0 and 60°C. Hydrolysis of cDPG occurred under nitrogen or hydrogen atmosphere and was completely inhibited by oxygen. Phosphate and potassium chloride were also strong inhibitors: 50% inhibition occurred at 0.6–0.7 mM phosphate or 0.2 M KCl. The enzyme was localized in the membrane fraction and could be solubilized for approximately 60% by treatment with 25 mM of the detergent CHAPS. The K m and the V max for cDPG were determined at 60°C and were 59 mM and 216 mU/mg, respectively. Furthermore, cDPG hydrolase was dependent on the presence of Co2+. The role of cDPG and cDPG hydrolase is discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-072X
    Keywords: Methanogenic bacteria ; Methanobacterium thermoautotrophicum ; ATP synthesis ; 2,3-Diphosphoglycerate ; 2,3-Diphosphoglycerate phosphatase ; Cyclic 2,3-diphosphoglycerate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell-free extracts of Methanobacterium thermoautotrophicum were found to catalyze ATP synthesis from an endogeneous substrate. Synthesis was stimulated under hydrogen atmosphere and inhibited by KCL (K i =150 mM). Comparison of the properties of a number of cell constituents showed the endogeneous substrate to be 2,3-diphosphoglycerate. The compound is converted into 3-phosphoglycerate, and via 2-phosphoglycerate and phosphoenolpyruvate into pyruvate, at which the latter reaction is linked with ATP synthesis.
    Type of Medium: Electronic Resource
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