Influence of 3-methylanthranilic and anthranilic acids on the formation of tryptophan synthetase in Escherichia coli.

It is now well recognized that the product of a series of biosynthetic reactions can play an important controlling role in its formation, either by inhibiting the activity or the formation of the enzymes concerned with its synthesis (Vogel, 1957; Pardee, 1959). Since the extent of such control is largely dependent on the intracellular concentration of the particular metabolite involved, the levels of enzyme function or formation can be controlled by manipulations which affect the intracellular concentrations of the repressing substance (Gorini and Maas, 1957). Thus, cultures grown in the presence of high concentrations of a particular repressor show a depressed content of the enzymes concerned with its synthesis. On the other hand, the maintenance of low levels of repressor, by controlled low level feeding to strains with a requirement for the repressing metabolite, results in an elevated enzyme level in such cultures. In some strains which have a partial block in the synthesis of a repressor the level of the corresponding enzymes is also high (Yanofsky, 1960). The latter observation suggests that specific inhibitors of reactions leading to repressor synthesis might be employed to control enzyme formation. This paper deals with an examination of this possibility with the tryptophan-synthesizing system of Escherichia coli, which is well suited for such a study. Tryptophan represses the formation of tryptophan synthetase in Aerobacter aerogenes (Monod and CohenBazire, 1953) as well as other enzymes involved in tryptophan synthesis in E. coli (Yanofsky, 1960). Contrariwise, strains which appear to be partially blocked in tryptophan synthesis, as evidenced by the stimulation of growth by