SUMMARY: grown on glucose or glutamate at 1 or 20 °, or on acetate at 20 °, as sole carbon sources, contained both pyruvate carboxylase and phosphoenolpyruvate carboxylase. Pyruvate carboxylase was insensitive to acetylcoenzyme A and L-aspartate, and its level in cell-free extracts was markedly dependent on the carbon source for growth, the highest specific activity being attained in glucose-grown cells. Phosphoenolpyruvate carboxylase, on the other hand, although less dependent on the nature of the carbon source, showed its highest level in acetate-grown cells; the enzyme activity required acetyl-coenzyme A and was strongly inhibited by L-aspartate. The micro-organism had, in addition, a phosphoenolpyruvate carboxykinase, which showed its highest specific activity in cells grown on acetate, and a NADP-linked malate enzyme, apparently repressed by acetate and showing its highest specific activity in glutamate-grown cells.


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