title: tyrR, a regulatory gene of tyrosine biosynthesis in Salmonella typhimurium.
abstract: 4-Fluorophenylalanine-resistant mutants of Salmonella typhimurium were isolated in which tyrosine pathway enzymes were not repressed by l-tyrosine. The mutants produced elevated levels of 3-deoxy-d-arabinoheptulosonic acid 7-phosphate (DAHP) synthetase (tyr) and chorismate mutase T-prephenate dehydrogenase, and these enzymes as well as transaminase A were not repressed by high concentrations of tyrosine. Genetic analysis revealed that a mutation in a gene designated tyrR was responsible for the constitutivity of the tyrosine pathway enzymes in strains SG1, SG7, and SG9, and that tyrR was linked to pyrF. In strain SG1 a mutation had also occurred in aroF, the structural gene for DAHP synthetase (tyr), resulting in loss of sensitivity of this enzyme to end-product inhibition. There appeared to be no relationship between loss of feedback inhibition and loss of end-product repression, since derivative strains of SG1 that carried only the tyrR mutation behaved like the singly mutated tyrR strains, SG7 and SG9, in showing high constitutive levels of tyrosine-specific enzymes that were not repressed by tyrosine.
mesh_terms: D000446:Aldehyde-Lyases / Q000096:biosynthesis; D002474:Cell-Free System; D002874:Chromosome Mapping; D003227:Conjugation, Genetic; D003509:Cyclohexanecarboxylic Acids; D004794:Enzyme Repression; D005461:Fluorine / Q000494:pharmacology; D005796:Genes; D005809:Genes, Regulator; D008040:Genetic Linkage; D010088:Oxidoreductases / Q000096:biosynthesis; D010649:Phenylalanine / Q000096:biosynthesis / Q000494:pharmacology; D010770:Phosphotransferases / Q000096:biosynthesis; D011773:Pyruvates; D011995:Recombination, Genetic; D012486:Salmonella typhimurium / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013237:Stereoisomerism; D014161:Transduction, Genetic; D014443:Tyrosine / Q000096:biosynthesis* / Q000494:pharmacology; D014444:Tyrosine Transaminase / Q000096:biosynthesis
chemical_list: D003509:Cyclohexanecarboxylic Acids; D011773:Pyruvates; D005461:Fluorine; D014443:Tyrosine; D010649:Phenylalanine; D010088:Oxidoreductases; D014444:Tyrosine Transaminase; D010770:Phosphotransferases; D000446:Aldehyde-Lyases