Control of Uracil Synthesis by Arginine in Escherichia Coli.

Ben-Ishai, Ruth (Israel Institute of Technology, Haifa), Michal Lahav, and Ada Zamir. Control of uracil synthesis by arginine in Escherichia coli. J. Bacteriol. 87:1436-1442. 1964.-It is shown that arginine affects uracil biosynthesis in Escherichia coli. The effect of arginine on uracil synthesis was analyzed by following the changes in the level of aspartate transcarbamylase, the first specific enzyme in uracil synthesis. In this research, an effect of arginine on aspartate transcarbamylase formation was observed only if the bacteria were preincubated with arginine in the presence of uracil analogues that cause apparent partial derepression of this enzyme. The possible effect of a structural modification of aspartate transcarbamylase by 2-thiouracil, the analogue principally used, is considered. However, it is shown that arginine causes derepression of aspartate transcarbamylase, even if a modification of the enzyme occurs. An effect of uracil on arginine synthesis can also be observed in repressible strains of E. coli, if conditions of partial derepression of the enzymes involved in arginine synthesis prevail. However, neither the derepression of aspartate transcarbamylase by arginine nor the derepression of ornithine transcarbamylase by uracil is accompanied by changes in the level of carbamyl phosphokinase, the enzyme that catalyzes carbamyl phosphate synthesis.