Skip Navigation

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Request Permissions
Google Scholar
Right arrow Articles by SHIIO, I.
Right arrow Articles by SUGIMOTO, S.-i.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by SHIIO, I.
Right arrow Articles by SUGIMOTO, S.-i.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

J. Biochem, 1978, Vol. 83, No. 3 879-886
© 1978 Japanese Biochemical Society

research-article

Altered Regulatory Mechanisms for Tryptophan Synthesis in Fluorotrptophan-Resistant Mutants of Brevibacterium flavum

Isamu SHIIO and Shin-ichi SUGIMOTO

Central Research Laboratories, Ajinomoto Co., Inc., Kawasaki-ku Kawasaki, Kanagawa 210

5-Fluorotryptophan (5FT) inhibited the activity of anthranilate synthetase (AS) of Brevi-bacterium flavum as strongly as did tryptophan. The concentration of 5FT required for complete inhibition of AS was similar to that for growth inhibition. Higher concentrations of 5FT repressed the synthesis of the tryptophan enzymes with a non-coordinate relationship between AS or anthranilate-phosphoribosylpyrophosphate phosphoribosylransferase (PRT) and indole-3-glycerol phosphate synthetase (InGPS) or tryptophan synthetase (TS)-B. In a mutant resistant to low concentrations of 5FT, strain 251, which produced anthranilate and had an AS less sensitive to feedback inhibition by tryptophan, all the tryptophan enzymes showed normal levels. On the other hand, in a mutant resistant to higher concentrations of 5FT, which was derived from strain 251 and produced L-tryptophan, the synthesis of all the tryptophan enzymes except PRT had been derepressed. In mutants resistant to high concentrations of 5FT, strains 1288 and 399, which were derived directly from the wild-type strain and produced L-tryptophan, the syntheses of all the tryptophan enzymes and of all except TS had been derepressed, respectively, in addition to desensitization of AS to feedback inhibition. From these results, it was concluded that the syntheses of the five enzymes in the tryptophan pathway are regulated independently of each other in B. flavum and that derepression of PRAI and of InGPS, as well as desensitization of AS to feedback inhibition, is essential for tryptophan overproduction. Among L-tryptophan-producing mutants, the amount of L-tryptophan produced depended on the extent of desensitization of AS rather than the specific activities of the derepressed enzymes.


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.