Feneant M, Moatti N, Maccario J, Gautier M, Guerroui S, Lemonnier A
Biochem J. 1984 Nov 15;224(1):309-15. doi: 10.1042/bj2240309.
The influence of cycloleucine on kinetic parameters of uptake of L-alanine, L-proline and L-leucine into cultured human fibroblasts was examined under initial-rate conditions with substrate concentrations of 0.05-10 mM and 5 mM-cycloleucine. Kinetic data obtained by computer analysis showed that, in the absence of cycloleucine, cell uptake was heterogeneous for each amino acid. L-Alanine and L-leucine entered by two transport systems with different affinities; L-proline was taken up by one saturable transport system plus a diffusion-like process. This heterogeneity disappeared in the presence of cycloleucine, since the high-affinity systems were no longer detectable. The remaining process had the same kinetic constants as the low-affinity system for alanine and leucine and a KD similar to the diffusion constant for proline. The influence of cycloleucine on the amino acid uptake was not specific either to the amino acid concerned or to a particular transport system, since the three neutral amino acid-transport systems, A, ASC and L, were involved in these experiments. This influence was shown to be unaffected by the absence of Na+ (for leucine uptake). ATP content of the cells was identical in the presence or in the absence of cycloleucine.
在底物浓度为0.05 - 10 mM以及5 mM环亮氨酸的初速率条件下，研究了环亮氨酸对培养的人成纤维细胞摄取L - 丙氨酸、L - 脯氨酸和L - 亮氨酸动力学参数的影响。通过计算机分析获得的动力学数据表明，在不存在环亮氨酸的情况下，每种氨基酸的细胞摄取是异质性的。L - 丙氨酸和L - 亮氨酸通过两种具有不同亲和力的转运系统进入细胞；L - 脯氨酸通过一种可饱和的转运系统以及类似扩散的过程被摄取。在存在环亮氨酸的情况下，这种异质性消失了，因为高亲和力系统不再可检测到。剩余的过程对于丙氨酸和亮氨酸具有与低亲和力系统相同的动力学常数，并且对于脯氨酸具有与扩散常数相似的解离常数（KD）。环亮氨酸对氨基酸摄取的影响既不是针对所涉及的氨基酸，也不是针对特定的转运系统，因为在这些实验中涉及了三种中性氨基酸转运系统，即A、ASC和L。这种影响被证明不受Na⁺缺失（对于亮氨酸摄取）的影响。在存在或不存在环亮氨酸的情况下，细胞的ATP含量是相同的。
