Physiological Role of Tryptophanase in Control of Tryptophan Biosynthesis in Bacillus alvei

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Abstract
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 μg/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.