White M F, Gazzola G C, Christensen H N
J Biol Chem. 1982 Apr 25;257(8):4443-9.
Cationic amino acid transport into human skin fibroblasts occurs by a saturable mediation which we designate System y+, which may prove identical with the earlier Ly. This plasma membrane agency is kinetically distinguishable from systems transporting neutral and acidic amino acids and serves to catalyze the flows of omega-guanidino amino acids and alpha, omega-diamino acids. Uptake of cationic substrates by System y+ is Na+-independent, pH-insensitive, stereoselective, and inhibitable by neutral amino acids in the presence of Na+. Uptake and exodus of System y+ substrates are strongly stimulated by cationic amino acids inside and outside the cell, respectively. Arginine and homoarginine accumulate in human fibroblasts reaching distribution ratios of more than 20 at external amino acid concentrations in the physiological range.
阳离子氨基酸进入人皮肤成纤维细胞是通过一种可饱和介导进行的，我们将其命名为y+系统，它可能与早期的Ly相同。这种质膜机制在动力学上与转运中性和酸性氨基酸的系统不同，可催化ω-胍基氨基酸和α,ω-二氨基酸的流动。y+系统对阳离子底物的摄取不依赖于Na+，对pH不敏感，具有立体选择性，在有Na+存在时可被中性氨基酸抑制。y+系统底物的摄取和外流分别受到细胞内外阳离子氨基酸的强烈刺激。在生理范围内的外部氨基酸浓度下，精氨酸和高精氨酸在人成纤维细胞中积累，分布比超过20。
