Growth of Pseudomonas acidovorans in the presence of l-tryptophan resulted in the appearance of a tryptophan transport system which was extremely sensitive to sodium azide or 2,4-dinitrophenol. Asparagine-grown cells possessed no detectable tryptophan “permease” activity. Substitution of l-kynurenine for l-tryptophan in the growth medium also induced the tryptophan permease activity, along with tryptophan oxygenase and kynurenine formamidase. This is the first reported example of the product induction of a permease activity. Irrespective of whether Pseudomonas cells are grown in the presence of d- or l-tryptophan, the resulting induced tryptophan permease activity is specific for the l-isomer. In addition, the radioactive compounds l-leucine, l-phenylalanine, or dl-5-hydroxytryptophan are not transported. When dl-5-fluorotryptophan is a component of the inducing medium (with l-tryptophan), induction of tryptophan permease activity, as well as tryptophan oxygenase, is inhibited. In the permease assay system, using normally induced cells, the fluoroanalogue inhibited strikingly tryptophan transport. Therefore, this analogue may inhibit induction by blocking inducer transport into the cell. When added to the l-tryptophan-inducing medium, dl-7-azatryptophan markedly enhanced induction of tryptophan oxygenase, but the level of tryptophan permease activity was not further elevated. The mechanism of this analogue is unclear at present. Invariant tryptophan permease activity levels are found in cells grown with 5 or 15 mml-tryptophan or 5 mm class="small-caps">l-kynurenine, whereas the respective tryptophan oxygenase levels are greatly different. Together with other results, these results indicate that the synthesis of tryptophan permease activity is not coordinate with that of tryptophan oxygenase. Tryptophan transport is strongly inhibited by class="small-caps">l-formylkynurenine and by class="small-caps">l-kynurenine. These two metabolites were prepared in radioactive form, and they are actively transported following bacterial growth on class="small-caps">l-tryptophan or class="small-caps">l-kynurenine. Preliminary results suggest the tryptophan permease activity may be distinct from the permease(s) activity for class="small-caps">l-formylkynurenine and class="small-caps">l-kynurenine. Kynurenine, then, is capable of inducing tryptophan permease and kynurenine permease activities.
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机译:在1-色氨酸存在下嗜酸假单胞菌的生长导致色氨酸转运系统的出现,该系统对叠氮化钠或2,4-二硝基苯酚极为敏感。天冬酰胺生长的细胞不具有可检测的色氨酸“通透酶”活性。在生长培养基中用L-犬尿氨酸取代L-色氨酸还诱导了色氨酸通透酶活性,以及色氨酸加氧酶和犬尿氨酸甲酰胺酶。这是渗透酶活性产物诱导的第一个报道的例子。不论假单胞菌细胞是在d色氨酸还是l色氨酸存在下生长,所产生的色氨酸通透酶活性都对l异构体具有特异性。另外,不转运放射性化合物1-亮氨酸,1-苯丙氨酸或dl-5-羟基色氨酸。当dl-5-氟色氨酸是诱导培养基(带有1-色氨酸)的成分时,色氨酸通透酶活性以及色氨酸加氧酶的诱导被抑制。在渗透酶分析系统中,使用正常诱导的细胞,氟类似物显着抑制了色氨酸的转运。因此,该类似物可通过阻止诱导剂转运进入细胞来抑制诱导。当添加到1-色氨酸诱导培养基中时,dl-7-氮杂色氨酸显着增强了色氨酸加氧酶的诱导,但是色氨酸通透酶活性的水平没有进一步提高。目前该类似物的机制尚不清楚。在用5或15 mml-色氨酸或5 mm的1-kynurenine生长的细胞中发现了不变的色氨酸通透酶活性水平,而各个色氨酸加氧酶水平却大不相同。与其他结果一起,这些结果表明色氨酸通透酶活性的合成与色氨酸加氧酶的合成不协调。色氨酸转运被 class =“ small-caps”> l span>-甲酰基尿氨酸和 class =“ small-caps”> l span> -kynurenine强烈抑制。这两种代谢物均以放射性形式制备,并且在细菌生长后在 class =“ small-caps”> l span>-色氨酸或 class =“ small-caps”> l span >-犬尿氨酸。初步结果表明,色氨酸通透酶活性可能不同于 class =“ small-caps”> l span> -formylkynurenine和 class =“ small-caps”> l span的通透酶活性。 >-犬尿氨酸。然后,Kynurenine能够诱导色氨酸通透酶和犬尿氨酸通透酶活性。
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