Acetate metabolism in Escherichia coli

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Abstract
Levels of several intermediary metabolites were measured in cells grown in acetate medium to test the hypothesis that the glyoxylate cycle is repressed by phosphoenolpyruvate (PEP). Wild-type cells had less PEP than either isocitrate dehydrogenase - deficient cells (which had greater isocitrate lyase activity than the wild type) or isocitrate dehydrogenase - deficient, citrate synthase - deficient cells (which are poorly inducible). Thus induction of the glyoxylate cycle is more complicated than a simple function of PEP concenration. No correlation between enzyme activity and the level of oxaloacetate, pyruvate or citrate was found either. Citrate was synthesized in citrate synthase - deficient mutants, possibly via citrate lyase.