BIOSYNTHESIS OF VALINE AND ISOLEUCINE, VI. ENZYME REPRESSION IN SALMONELLA

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Abstract
There is no feedback-control mechanism for the isoleucine-valine pathway of S. typhimurium. However, there is repression of reductoisomerase and the [alpha],[beta]-dihydroxyacid-dehydrase. The effect that valine, isoleucine and leucine (alone or in combination) have on the repression of the pathway was studied under various experimental conditions. The results show that the "multi-valent" coordinated repression described for the pathway in mutant strains is not observed in wild-type, and it is proposed that the true repression mechanism is a phenomenon more complex than the described "multi-valent" repression.