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首页> 外文期刊>Journal of bacteriology >Sodium-dependent transport of L-leucine in membrane vesicles prepared from Pseudomonas aeruginosa.
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Sodium-dependent transport of L-leucine in membrane vesicles prepared from Pseudomonas aeruginosa.

机译：L-亮氨酸在铜绿假单胞菌制备的膜囊泡中的钠依赖性转运。

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摘要

Membrane vesicles were prepared by osmotic lysis of spheroplasts of Pseudomonas aeruginosa strain P14, and the active transport of amino acids was studied. D-Glucose, gluconate, and L-malate supported active transport of various L-amino acids. The respiration-dependent leucine transport was markedly stimulated by Na+. Moreover, without any respiratory substrate, leucine was also transported transiently by the addition of Na+ alone. This transient uptake of leucine was not inhibited either by carbonyl cyanide p-trifluoromethyoxyphenylhydrazone or by valinomycin, but was completely abolished by gramicidin D. Increase in the concentration of Na+ of the medium resulted in a decrease of the Km for L-leucine transport, whereas the Vmax was not significnatly affected. Active transport of leucine was inhibited competitively by isoleucine or by valine, whose transport was also stimulated by Na+. On the other hand, Na+ was not required for the uptake of other L-amino acids tested, but rather was inhibitory for some of them. These results show (i) that a common transport system for branched-chain amino acids exists in membrane vesicles, (ii) that the system requires Na+ for its activity, and (iii) that an Na+ gradient can drive the system.
机译：通过铜绿假单胞菌菌株P14的原生质体渗透裂解制备膜囊泡，并研究了氨基酸的主动转运。 D-葡萄糖，葡萄糖酸和L-苹果酸支持各种L-氨基酸的主动转运。依赖呼吸的亮氨酸转运被Na +明显刺激。而且，在没有任何呼吸底物的情况下，亮氨酸也可以通过单独添加Na +瞬时转运。亮氨酸的这种瞬时吸收不会被羰基氰对三氟甲氧基苯hydr或缬氨霉​​素抑制，而是被短杆菌肽D完全消除。培养基中Na +浓度的增加导致L-亮氨酸转运的Km降低，而Vmax并未受到明显影响。亮氨酸的主动转运被异亮氨酸或缬氨酸竞争性抑制，其转运也受到Na +的刺激。另一方面，摄取其他测试的L-氨基酸并不需要Na +，而是对其中某些氨基酸具有抑制作用。这些结果表明（i）膜小泡中存在一个常见的支链氨基酸转运系统，（ii）该系统需要Na +才能发挥其活性，并且（iii）Na +梯度可以驱动该系统。

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