AN INDUCIBLE TRYPTOPHAN SYNTHETASE IN TRYPTOPHAN AUXOTROPHS OF ESCHERICHIA COLI

Publisher Website
Google Scholar
Abstract
Tryptophan-re-quiring mutants of 3 different strains of E. coli contain a tryptophan synthetase (TSase) that is induced by high concentrations of tryptophan. The inducible nature of the enzyme is responsible for the inability of indole to substitute for tryptophan in growth of the mutants. The inducible TSase catalyzes synthesis of tryptophan from indole plus serine but not from indoleglycerol-phosphate plus serine, and it does not hydrolyze indoleglycerol-phosphate. This indicates that this enzyme is different from either the A or the B component of the repressible TSase of E. coli. A single mechanism may control the synthesis of 2 distinct proteins responsible for the 2 activities or a single protein may possess both catalytic activities.