Isolation and partial characterization of an argR mutant of Salmonella typhimurium

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Abstract
An arginine regulatory mutant (i.e., mutated in the argR gene) was isolated from a strain of S. typhimurium LT2. The argR mutant excreted arginine into the growth medium with glycerol but not glucose as C source. Constitutive synthesis of arginine biosynthetic enzymes [N-acetylornithine-.delta.-transaminase EC 2.6.1.11, N-acetylornithinase EC 3.5.1.16, and orinithine transcarbamylase (OTCase) EC 2.1.3.3] was observed. Whereas previous results showed constitutive synthesis of carbamyl phosphate synthetase [EC 2.7.2.5] in the argR mutant, the regulation of the synthesis of the last 5 enzymes [aspartate transcarbamylase EC 2.1.3.2, dihydroorotase EC 3.5.2.3, dihydroorotate dehydrogenase EC 1.3.3.1, orotidine monophosphate pyrophosphorylase EC 2.4.2.10, and orotidine monophosphate decarboxylase EC 4.1.1.23] of the pyrimidine pathway was unaffected. In pyrH mutants known to exhibit derepressed synthesis of the pyrimidine enzymes, a 10-fold derepression of OTCase was observed.