Physiological role of tryptophanase in control of tryptophan biosynthesis in Bacillus alvei.

Hoch, J. A. (University of Illinois, Urbana), and R. D. DeMoss. Physiological role of tryptophanase in control of tryptophan biosynthesis in Bacillus alvei. J. Bacteriol. 91:667-672. 1966.-Indole excretion occurred early in the exponential growth phase, and derived mainly from biosynthetic intermediates of tryptophan. Tryptophan cleavage by tryptophanase contributed about 1.5% of the indole excreted. In the presence of exogenous tryptophan (5 to 10 mug/ml), excretion of early indole was not observed. Experiments with isotopically labeled indole and tryptophan showed that a low rate of endogenous tryptophan biosynthesis occurred constantly during growth. Both exogenously and endogenously supplied tryptophan were degraded by tryptophanase. As a consequence, the intracellular tryptophan concentration appeared to be maintained at a constant low level. It was suggested that the action of tryptophanase is an example of an enzymatic mechanism which controls the level of a specific metabolite pool.