Young J D, Ellory J C
J Neural Transm Suppl. 1979(15):139-51. doi: 10.1007/978-3-7091-2243-3_12.
Mammalian erythrocytes are known to have 4 distinct amino acid transport systems. The C system is found in sheep erythrocytes and is specific for neutral amino acids of intermediate size. Human cells lack the C system and have two alternative neutral amino acid transport mechanisms: the L system which is selective for large hydrophobic amino acids and a Na-dependent alanine-cysteine system. The L system is absent from ruminant and cat erythrocytes. Human rabbit and cat cells, but not sheep erythrocytes, have a specific dibasic amino acid transport mechanism (Ly system). L-Tryptophan uptake by human erythrocytes is mediated by two routes: a saturable high-affinity transport mechanism selective for L-tryptophan and a low affinity uptake mediated by the L system. The saturable component of L-tryptophan transport occurs by a previously unidentified uptake system, and is the major route for L-tryptophan uptake at physiological substrate concentrations. This system is absent from sheep and cat erythrocytes.
已知哺乳动物红细胞有4种不同的氨基酸转运系统。C系统存在于绵羊红细胞中，对中等大小的中性氨基酸具有特异性。人类细胞缺乏C系统，有两种替代的中性氨基酸转运机制：对大的疏水性氨基酸有选择性的L系统和一种依赖钠的丙氨酸 - 半胱氨酸系统。反刍动物和猫的红细胞中不存在L系统。人类、兔和猫的细胞（但绵羊红细胞没有）有一种特定的二碱基氨基酸转运机制（Ly系统）。人类红细胞摄取L - 色氨酸有两条途径：一种对L - 色氨酸有选择性的可饱和高亲和力转运机制，以及由L系统介导的低亲和力摄取。L - 色氨酸转运的可饱和成分通过一种先前未鉴定的摄取系统发生，并且是生理底物浓度下L - 色氨酸摄取的主要途径。绵羊和猫的红细胞中不存在该系统。
