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Catabolic and Anabolic Enzyme Activities and Energetics of Acetone Metabolism of the Sulfate-Reducing Bacterium Desulfococcus biacutus

Catabolic and Anabolic Enzyme Activities and Energetics of Acetone Metabolism of the Sulfate-Reducing Bacterium Desulfococcus biacutus

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JANSSEN, Peter H., Bernhard SCHINK, 1995. Catabolic and Anabolic Enzyme Activities and Energetics of Acetone Metabolism of the Sulfate-Reducing Bacterium Desulfococcus biacutus. In: Journal of Bacteriology. 177(2), pp. 277-282

@article{Janssen1995Catab-6869, title={Catabolic and Anabolic Enzyme Activities and Energetics of Acetone Metabolism of the Sulfate-Reducing Bacterium Desulfococcus biacutus}, year={1995}, number={2}, volume={177}, journal={Journal of Bacteriology}, pages={277--282}, author={Janssen, Peter H. and Schink, Bernhard} }

deposit-license Acetone degradation by cell suspensions of Desulfococcus biacutus was CO2 dependent, indicating initiation by a carboxylation reaction, while degradation of 3-hydroxybutyrate was not CO2 dependent. Growth on 3-hydroxybutyrate resulted in acetate accumulation in the medium at a ratio of 1 mol of acetate per mol of substrate degraded. In acetone-grown cultures no coenzyme A (CoA) transferase or CoA ligase appeared to be involved in acetone metabolism, and no acetate accumulated in the medium, suggesting that the carboxylation of acetone and activation to acetoacetyl-CoA may occur without the formation of a free intermediate. Catabolism of 3-hydroxybutyrate occurred after activation by CoA transfer from acetyl-CoA, followed by oxidation to acetoacetyl-CoA. In both acetone-grown cells and 3-hydroxybutyrate-grown cells, acetoacetyl-CoA was thiolytically cleaved to two acetyl-CoA residues and further metabolized through the carbon monoxide dehydrogenase pathway. Comparison of the growth yields on acetone and 3-hydroxybutyrate suggested an additional energy requirement in the catabolism of acetone. This is postulated to be the carboxylation reaction (DG&* for the carboxylation of acetone to acetoacetate, 117.1 kJ z mol21). At the intracellular acyl-CoA concentrations measured, the net free energy change of acetone carboxylation and catabolism to two acetyl-CoA residues would be close to 0 kJ z mol of acetone21, if one mol of ATP was invested. In the absence of an energy-utilizing step in this catabolic pathway, the predicted intracellular acetoacetyl-CoA concentration would be 1013 times lower than that measured. Thus, acetone catabolism to two acetyl-CoA residues must be accompanied by the utilization of the energetic equivalent of (at least) one ATP molecule. Measurement of enzyme activities suggested that assimilation of acetyl-CoA occurred through a modified citric acid cycle in which isocitrate was cleaved to succinate and glyoxylate. Malate synthase, condensing glyoxylate and acetyl-CoA, acted as an anaplerotic enzyme. Carboxylation of pyruvate or phosphoenolpyruvate could not be detected. 2011-03-24T17:29:47Z Janssen, Peter H. First publ. in: Journal of Bacteriology 177 (1995), 2, pp. 277-282 eng 1995 Catabolic and Anabolic Enzyme Activities and Energetics of Acetone Metabolism of the Sulfate-Reducing Bacterium Desulfococcus biacutus application/pdf Schink, Bernhard Janssen, Peter H. Schink, Bernhard 2011-03-24T17:29:47Z

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