Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
Curr Top Membr. 2012;70:357-75. doi: 10.1016/B978-0-12-394316-3.00011-9.
Vitamin C (ascorbic acid) is required for the synthesis of collagen, carnitine, catecholamine and the neurotransmitter norepinephrine. Vitamin C also plays an important role in protection against oxidative stress. Transporters for vitamin C and its oxidized form dehydroascorbate (DHA) are crucial to keep vitamin concentrations optimal in the body. The human SLC23 family consists of the Na(+)-dependent vitamin C transporters SVCT1 (SLC23A1) and SVCT2 (SLC23A2) and the orphan transporter SVCT3 (SLC23A3). Phylogenetically, the SLC23 family belongs to the nucleobase-ascorbate transporter family although no specificity for nucleobases has yet been demonstrated for the human members of this family. In fact, the SVCT1 and SVCT2 transporters are rather specific for ascorbic acid. SVCT1 is expressed in epithelial tissues such as intestine, where it contributes to the maintenance of whole-body ascorbic acid levels, whereas the expression of SVCT2 is relatively widespread either to protect metabolically active cells and specialized tissues from oxidative stress or to deliver ascorbic acid to tissues that are in high demand of the vitamin for enzymatic reactions. DHA, the oxidized form of ascorbic acid is taken up and distributed in the body by facilitated transport via members of the SLC2/GLUT family (GLUT1, GLUT3, and GLUT4). Although, the main focus of this review is on the SLC23 family of ascorbic acid transporters, transporters of DHA and nucleobases are also briefly discussed for completeness.
维生素 C（抗坏血酸）是胶原蛋白、肉碱、儿茶酚胺和神经递质去甲肾上腺素合成所必需的。维生素 C 还在抗氧化应激中发挥重要作用。维生素 C 及其氧化形式脱氢抗坏血酸 (DHA) 的转运蛋白对于保持体内维生素浓度的最佳状态至关重要。人类 SLC23 家族由依赖 Na+的维生素 C 转运蛋白 SVCT1（SLC23A1）和 SVCT2（SLC23A2）以及孤儿转运蛋白 SVCT3（SLC23A3）组成。从系统发生的角度来看，SLC23 家族属于核苷-抗坏血酸转运家族，尽管尚未证明该家族的人类成员具有核苷特异性。事实上，SVCT1 和 SVCT2 转运蛋白对抗坏血酸具有相当的特异性。SVCT1 表达在肠道等上皮组织中，有助于维持全身抗坏血酸水平，而 SVCT2 的表达相对广泛，无论是为了保护代谢活跃的细胞和特化组织免受氧化应激，还是为了将抗坏血酸输送到对酶反应有高需求的组织。DHA，抗坏血酸的氧化形式，通过 SLC2/GLUT 家族（GLUT1、GLUT3 和 GLUT4）的易化转运在体内被摄取和分布。尽管本综述的重点是抗坏血酸的 SLC23 家族转运蛋白，但为了完整性，也简要讨论了 DHA 和核苷的转运蛋白。
