Repression by glucose of acetohydroxy acid synthetase in Escherichia coli B

Abstract

Acetolactate formation in Escherichia coli B results from the activity of a single system, acetohydroxy acid synthetase, which has a pH optimum of 8.0 and is sensitive to end-product inhibition by l-valine. Acetohydroxy acid synthetase was found to be subject to catabolite repression, and the nature and concentration of the carbon source had a greater effect on the formation of the enzyme than had the known end products (valine, isoleucine, leucine and pantothenate) of the biosynthetic pathways of which this enzyme is a member. The results suggest that acetohydroxy acid synthetase may play an amphibolic role in E. coli B.

Relaxation of catabolite repression and loss of valine sensitivity in Escherichia coli K‐12

“…As reported previously [5] the AHAS of E. coli B is subject to catabolite repression. Since the growth of E. coli B in minimal medium is not inhibited in the presence of valine this strain presumably contains AHAS I and II, either or both of which may be sensitive to catabolite repression [5].…”

“…As reported previously [5] the AHAS of E. coli B is subject to catabolite repression. Since the growth of E. coli B in minimal medium is not inhibited in the presence of valine this strain presumably contains AHAS I and II, either or both of which may be sensitive to catabolite repression [5]. In the present work, we have established that the (single) AHAS activity of E. coli K-l 2 is sensitive to catabolite repression and that relaxation of this control permits cell growth in the presence of valine.…”

Repression of Acetolactate Synthetase by Glucose inAerobacter aerogenes

“…Similar results were obtained in phosphate sufficient medium. Thus, the catabolite repression of AHAsr by glucose was not found in A. aerogenes [1][2][3][4][5][6][7][8][9][10][11][12].…”

“…1i It was found in Escherichia coli B and Salmonella typhimurium that repression of AHASs was multivalent and required the presence of leucine and isoleucine in addition to valine. 3 …”

“…3 ) In view of the regulatory mechanism by carbon source, similarity existed between the nature of E. coli AHASs and that of ALS. However, no repression of ALS formation was observed in the presence of end-products (Table III).…”