Formation and Interrelationships of Tryptophanase and Tryptophan Synthetases in Escherichia coli
AUTOR(ES)
Newton, W. Austin
RESUMO
Newton, W. Austin (University of California, Berkeley), and Esmond E. Snell. Formation and interrelationships of tryptophanase and tryptophan synthetases in Escherichia coli. J. Bacteriol. 89:355–364. 1965.—In addition to the classical tryptophan-repressible tryptophan synthetase (TSase-tr), tryptophan auxotrophs of Escherichia coli contain another distinct tryptophan synthetase (TSase-ti) which is induced by tryptophan and is identical with tryptophanase (TPase). Escherichia coli B (wild type) forms only TSase-tr when the growth medium lacks tryptophan. When tryptophan is supplied, parallel induction of TPase and TSase-ti occurs while TSase-tr is repressed. Antiserum prepared against purified TPase neutralized TPase and TSase-ti equally, but not TSase-tr. TPase-negative strains of E. coli do not form TSase-ti. Unlike TSase-tr, TSase-ti is not readily detected by whole-cell assays. In the tryptophan auxotroph, E. coli B/1t7, a direct correlation exists between the effectiveness of 4-, 5-, and 6-methyl-tryptophan in inducing TPase and in promoting growth in the presence of indole. In a mutant of this organism, E. coli B/1t7-A, which is constitutive for TPase, 5-methyl-tryptophan and other substrates of TPase increased the rate of growth on limiting indole, a result ascribed to their ability to inhibit degradation of tryptophan and to supply the 3-carbon side chain for synthesis of tryptophan by TPase. This organism produced maximal amounts of TPase when inocula from log-phase cells grown in tryptophan-supplemented minimal medium were allowed to undergo two cell generations in an enriched broth medium.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=305515Documentos Relacionados
- TRYPTOPHANASE-TRYPTOPHAN SYNTHETASE SYSTEMS IN ESCHERICHIA COLI I. : Effect of Tryptophan and Related Compounds
- Physiological studies of tryptophan transport and tryptophanase operon induction in Escherichia coli.
- TRYPTOPHANASE-TRYPTOPHAN SYNTHETASE SYSTEMS IN ESCHERICHIA COLI II. : Effect of Glucose
- TRYPTOPHANASE-TRYPTOPHAN SYNTHETASE SYSTEMS IN ESCHERICHIA COLI III. : Requirements for Enzyme Synthesis
- Inhibition of the Induced Formation of Tryptophanase in Escherichia coli by Near-Ultraviolet Radiation