Formation of Tryptophansynthase and its Regulation during the Active Growth Phases of Escherichia coli.

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Abstract
The formation of tryptophansynthase by Escherichia coli was investigated in cells that were transferred from a medium containing amino-acids and vitamins to a simple glucose-mineral salt medium. A maximal repression of enzyme formation was effected by tryptophan in concentrations of 75[long dash]100 [mu][image]; concentrations of 35[long dash]45 [mu][image], repressed the formation to 50%. The amount of tryptophansynthase formed increased 10[long dash]15-fold; but in cells with a high initial activity at the beginning of the lag phase, the increase was only about 1.5-fold. The repression took effect immediately when L-tryptophan in 0.5 m[image] concentration was added to the medium containing the E. coli cellsTn the lag phase. A high tryptophanase activity in the cells caused an increase in the formation of tryptophansynthase. Indole inhibited the formation.

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