Rosenberg R
J Neural Transm Suppl. 1979(15):153-60. doi: 10.1007/978-3-7091-2243-3_13.
Some results from ongoing studies of the transport of some neutral amino acids across the human erythrocyte membrane (L-tryptophan and L-leucine) at 25 degrees C are presented. The unidirectional flux into the cell at initial rate as a function of the substrate concentration can be described by a 3-parameter model (i.e. a carrier in parallel with an apparent leak component). From the estimated kinetic parameters an apparent membrane permeability of the carrier (substrate concentrations S1 smaller than Kzt 12) has been calculated. The permeability of L-tryptophan (1.03 . 10(-8) cm/sec) was significantly lower than the permeability of L-leucine (2.36 . 10(-7) cm/sec). The contribution of the leak permeability to the total permeability at low concentrations was about 10% for L-tryptophan, but only 1% for L-leucine. From inhibition studies it is indicated that L-tryptophan passing the membrane via theapparent leak component is transported by the L-leucine carrier, the affinity being low. The saturable component of L-tryptophan transport does not correspond to any known amino acid transport system, and it is thus strongly suggested that a new L-tryptophan specific transport system operating at physyological concentrations has been described.
本文展示了一些正在进行的关于某些中性氨基酸（L-色氨酸和L-亮氨酸）在25摄氏度下跨人红细胞膜转运研究的结果。初始速率下单向流入细胞的通量作为底物浓度的函数可用一个三参数模型来描述（即一个载体与一个表观渗漏成分并联）。根据估算的动力学参数，已计算出载体的表观膜通透性（底物浓度S1小于Kzt 12）。L-色氨酸的通透性（1.03×10⁻⁸厘米/秒）显著低于L-亮氨酸的通透性（2.36×10⁻⁷厘米/秒）。在低浓度下，渗漏通透性对总通透性的贡献，L-色氨酸约为10%，而L-亮氨酸仅为1%。抑制研究表明，通过表观渗漏成分穿过膜的L-色氨酸由L-亮氨酸载体转运，亲和力较低。L-色氨酸转运的可饱和成分与任何已知的氨基酸转运系统均不对应，因此强烈提示已描述了一种在生理浓度下起作用的新的L-色氨酸特异性转运系统。
