Willis R C, Iwata K K, Furlong C E
J Bacteriol. 1975 Jun;122(3):1032-7. doi: 10.1128/jb.122.3.1032-1037.1975.
The formation of the high-affinity (Km equal to 0.2 muM) L-glutamine transport system of Escherichia coli strain 7 (Lin) appears to be subject to the same major control as the glutamine synthetase (EC 6.3.1.2) of this gram-negative organism. Culture of cells under nitrogen-limited conditions provides maximum derepression of both the glutamine synthetase and the glutamine transport system. Nutritional conditions providing a rich supply of ammonium salts or available sources of nitrogen, i.e., conditions which repress the formation of glutamine synthetase, provide three- and 20-fold repression, respectively, of the glutamine transport system. Culture of cells with glutamine supplements of 2 mM does not increase the repression of high-affinity glutamine transport system beyond the level observed in the absence of glutamine. A second kinetically distinct low-affinity component of glutamine. A second kinetically distinct low-affinity component of glutamine uptake is observed in cells cultured with a glutamine-depleted nutrient broth. This second component is associated with the appearance of glutaminase A (EC 3.5.1.2) and asparaginase I (EC 3.5.1.1), a periplasmic enzyme. Parallel changes were observed in the levels of the high-affinity glutamine transport system and the glutamine synthetase when cells were cultured with the carbon sources: glucose, glycerol, or succinate.
大肠杆菌7（Lin）株高亲和力（Km等于0.2 μM）L-谷氨酰胺转运系统的形成似乎与这种革兰氏阴性菌的谷氨酰胺合成酶（EC 6.3.1.2）受到相同的主要调控。在氮限制条件下培养细胞可使谷氨酰胺合成酶和谷氨酰胺转运系统达到最大程度的去阻遏。提供丰富铵盐或可用氮源的营养条件，即抑制谷氨酰胺合成酶形成的条件，分别使谷氨酰胺转运系统受到3倍和20倍的阻遏。用2 mM谷氨酰胺补充剂培养细胞，不会使高亲和力谷氨酰胺转运系统的阻遏程度超过在无谷氨酰胺情况下观察到的水平。谷氨酰胺摄取的第二个动力学上不同的低亲和力组分。在用谷氨酰胺耗尽的营养肉汤培养的细胞中观察到谷氨酰胺摄取的第二个动力学上不同的低亲和力组分。这第二个组分与谷氨酰胺酶A（EC 3.5.1.2）和天冬酰胺酶I（EC 3.5.1.1，一种周质酶）的出现相关。当用碳源葡萄糖、甘油或琥珀酸培养细胞时，在高亲和力谷氨酰胺转运系统和谷氨酰胺合成酶的水平上观察到平行变化。
