Synaptosomes isolated from adult rat cerebral cortices were used for studying the uptake of L-leucine by the Na(+)-dependent route. Three non-metabolizable amino acid analogues, which had been used previously to discriminate the Na(+)-dependent A-type uptake system of animal cells, were employed in this study. It was found that Na(+)-dependent uptake of leucine was insensitive to inhibition by 2-aminoisobutyric acid (AIB) and N-methylaminoisobutyric acid (MeAIB) whereas N-methylalanine (NMA) was markedly inhibitory. Inhibition by NMA was stereospecific--only the L-isomer had a pronounced effect. Na(+)-dependent uptake of leucine as well as its inhibition by L-NMA were rather insensitive to changes in pH from 6 to 9. Kinetic analysis of inhibition by L-NMA of Na(+)-dependent uptake revealed a non-competitive type of inhibition with a Ki value of approximately 0.5 mM.

译文

:从成年大鼠大脑皮层分离的突触体用于研究Na()依赖途径对L-亮氨酸的摄取。在这项研究中使用了三种不可代谢的氨基酸类似物,这些氨基酸类似物先前已用于区分动物细胞的Na(-)依赖性A型摄取系统。发现亮氨酸的Na()依赖性摄取对2-氨基异丁酸(AIB)和N-甲基氨基异丁酸(MeAIB)的抑制不敏感,而N-甲基丙氨酸(NMA)具有明显的抑制作用。 NMA的抑制作用是立体特异性的-只有L-异构体具有明显的作用。 Na()依赖性亮氨酸的摄取及其对L-NMA的抑制作用对pH值从6到9的变化不敏感。动力学分析表明L-NMA对Na()依赖性摄取的抑制作用揭示了一种非竞争性类型Ki值约为0.5 mM的抑制作用。

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