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Changes in the Intracellular Concentration of Acetyl-CoA and Malonyl-CoA in Relation to the Carbon and Energy Metabolism of Escherichia coli K12
Abstract
Intracellular concentrations of acetyl-CoA and malonyl-CoA in Escherichia coli K12 were determined by a malonyl-CoA:acetyl-CoA cycling technique. Under aerobic growth conditions with glucose the acetyl-CoA and malonyl-CoA concentrations varied over a range of 0.05-1.5 nmol (mg dry wt)-1 (20-600 μM) and 0·01-0·23 mol (mg dry wt)-1 (4·90 μm), respectively. The intracellular concentration of acetyl-CoA was highest in exponentially growing cells and it fell rapidly to less than 5% of the maximum level when the organism entered stationary phase after exhaustion of glucose. A linear relationship was observed between the intracellular concentration of total acyl-CoA and the logarithm of the concentration of glucose in the medium. Consequently, the acetyl-CoA/malonyl-CoA ratios also varied drastically, in a range of 0·6-41·7, under different conditions. Of several carbon sources tested, glucose was the most effective for promoting the synthesis of cellular acetyl-CoA. For cells grown on glycerol or acetate the maximum concentrations of total acyl-CoA were significantly lower. In cells incubated with citrate (not used as a carbon source by E. coli), the level was consistent with that in cells starved for exogenous carbon sources.
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© Society for General Microbiology 1988