TRYPTOPHANASE-TRYPTOPHAN SYNTHETASE SYSTEMS INESCHERICHIA COLIII

Freundlich, Martin (University of Minnesota, Minneapolis) and Herman C. Lichstein. Tryptophanase-tryptophan synthetase systems in Escherichia coli. II. Effect of glucose. J. Bacteriol. 84:988-995. 1962.-The effect of glucose and other compounds on the formation of tryptophanase and tryptophan synthetase in Escherichia coli was examined. Although most of these compounds were potent inhibitors of the synthesis of tryptophanase, they invariably increased the formation of tryptophan synthetase. The severity of tryptophanase inhibition depended upon the degree of utilization of the compound by the growing bacterial cells. It was found that high levels of tryptophan overcame by 40% the repression caused by glucose. The stimulatory effect of glucose on tryptophan synthetase formation in E. coli 9723E could be duplicated by indole-3-propionic acid. A study of the amino acid pool of E. coli 9723E revealed no free tryptophan in cells harvested from the basal medium containing glucose. In contrast, cells grown in the absence of glucose possessed a measurable amount of this amino acid. The possible mechanisms of the effect of glucose and related compounds on tryptophanase and tryptophan synthetase formation, as well as the relationship of these effects to the metabolic control of tryptophan metabolism, are discussed.