Gollub E G, Liu K P, Sprinson D B
J Bacteriol. 1973 Sep;115(3):1094-102. doi: 10.1128/jb.115.3.1094-1102.1973.
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.
分离出鼠伤寒沙门氏菌的4-氟苯丙氨酸抗性突变体，其中酪氨酸途径的酶不受L-酪氨酸的抑制。这些突变体中3-脱氧-D-阿拉伯庚酮糖酸7-磷酸（DAHP）合成酶（tyr）、分支酸变位酶T-预苯酸脱氢酶的水平升高，并且这些酶以及转氨酶A不受高浓度酪氨酸的抑制。遗传分析表明，在一个名为tyrR的基因中的突变导致了菌株SG1、SG7和SG9中酪氨酸途径酶的组成型表达，并且tyrR与pyrF连锁。在菌株SG1中，DAHP合成酶（tyr）的结构基因aroF也发生了突变，导致该酶对终产物抑制的敏感性丧失。反馈抑制的丧失和终产物阻遏的丧失之间似乎没有关系，因为仅携带tyrR突变的SG1衍生菌株的表现与单突变的tyrR菌株SG7和SG9相似，即显示出酪氨酸特异性酶的高组成型水平，且不受酪氨酸抑制。
