ISOLEUCINE AND VALINE METABOLISM IN ESCHERICHIA COLI XI. K-12

Abstract

Leavitt, Richard I. (Harvard Medical School, Boston, Mass.) and H. E. Umbarger . Isoleucine and valine metabolism in Escherichia coli . XI. Valine inhibition of the growth of Escherichia coli strain K-12. J. Bacteriol. 83: 624–630. 1962.—The inhibition of the growth of Escherichia coli strain K-12 by valine was shown to be due to the sensitivity of the acetohydroxybutyrate-forming system to valine. It was demonstrated that both E. coli strain W, a strain whose growth is unaffected by valine, and a valine-resistant mutant of strain K-12 have acetolactate- and acetohydroxybutyrate-forming systems which are less sensitive to valine than that of strain K-12. It was further shown that α-aminobutyrate accumulates in the culture fluid of the valine-sensitive strain when incubated in the presence of valine. The levels of valine in the “free amino acid pool” were examined and found to be related to the differences in valine sensitivity of the acetolactate-forming systems of the three strains.