Anaerobic acetate oxidation to CO2 by Desulfotomaculum acetoxidans |
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Authors: | Alfred M. Spormann Rudolf K. Thauer |
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Affiliation: | (1) Mikrobiologie, Fachbereich Biologie, Philipps-Universität, Karl-von-Frisch-Straße, D-3550 Marburg, Federal Republic of Germany |
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Abstract: | Desulfotomaculum acetoxidans has been proposed to oxidize acetate to CO2 via an oxidative acetyl-CoA/carbon monoxide dehydrogenase pathway rather than via the citric acid cycle. We report here the presence of the enzyme activities required for the operation of the novel pathway. In cell extracts the following activities were found (values in brackets=specific activities and apparent Km; 1 U·mg-1=1 mol·min-1·mg protein-1 at 37°C): Acetate kinase (6.3 U·mg-1; 2 mM acetate; 2.4 mM ATP); phosphate acetyltransferase (60 U·mg-1, 0.4 mM acetylphosphate; 0.1 mM CoA); carbon monoxide dehydrogenase (29 U·mg-1; 13% carbon monoxide; 1.3 mM methyl viologen); 5,10-methylenetetrahydrofolate reductase (3 U·mg-1, 0.06 mM CH3–FH4); methylenetetrahydrofolate dehydrogenase (3.6 U·mg-1, 0.9 mM NAD, 0.1 mM CH2=FH4); methenyltetrahydrofolate cyclohydrolase (0.3 U·mg-1); formyltetrahydrofolate synthetase (3 U·mg-1, 1.4 mM FH4, 0.4 mM ATP, 13 mM formate); and formate dehydrogenase (10 U·mg-1, 0.4 mM formate, 0.5 mM NAD). The specific activities are sufficient to account for the in vivo acetate oxidation rate of 0.26 U·mg-1.Non-standard abbreviations FH4 Tetrahydrofolate - CHO-FH4 N10-formyltetrahydrofolate - CHFH4 N5,N10-methenyltetrahydrofolate - CH2=FH4 N5,N10-methylenetetrahydrofolate - CH3–FH4 N5-methyltetrahydrofolate - MOPS morpholinopropane sulfonic acid - DTT d,l-1,4-dithiothreitol - TRIS tris-(hydroxymethyl)-aminomethane - Ap5A p1,P5-di(adenosine-5)pentaphosphate - MV methyl viologen |
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Keywords: | Desulfotomaculum Sulfate reduction Acetate oxidation Acetyl-CoA Carbon monoxide dehydrogenase Tetrahydrofolates Acetyl-CoA/carbon monoxide dehydrogenase pathway Citric acid cycle |
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