Vitamin C transport systems of mammalian cells

Mol Membr Biol. 2001 Jan-Mar;18(1):87-95. doi: 10.1080/09687680110033774.


Vitamin C is essential for many enzymatic reactions and also acts as a free radical scavenger. Specific non-overlapping transport proteins mediate the transport of the oxidized form of vitamin C, dehydroascorbic acid, and the reduced form, L-ascorbic acid, across biological membranes. Dehydroascorbic acid uptake is via the facilitated-diffusion glucose transporters, GLUT 1, 3 and 4, but under physiological conditions these transporters are unlikely to play a major role in the uptake of vitamin C due to the high concentrations of glucose that will effectively block influx. L-ascorbic acid enters cells via Na+-dependent systems, and two isoforms of these transporters (SVCT1 and SVCT2) have recently been cloned from humans and rats. Transport by both isoforms is stereospecific, with a pH optimum of approximately 7.5 and a Na+:ascorbic acid stoichiometry of 2:1. SVCT2 may exhibit a higher affinity for ascorbic acid than SVCT1 but with a lower maximum velocity. SVCT1 and SVCT2 are predicted to have 12 transmembrane domains, but they share no structural homology with other Na+ co-transporters. Potential sites for phosphorylation by protein kinase C exist on the cytoplasmic surface of both proteins, with an additional protein kinase A site in SVCT1. The two isoforms also differ in their tissue distribution: SVCT1 is present in epithelial tissues, whereas SVCT2 is present in most tissues with the exception of lung and skeletal muscle.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Ascorbic Acid / metabolism*
  • Biological Transport
  • COS Cells
  • Cations
  • Cell Membrane / metabolism
  • Cloning, Molecular
  • Dehydroascorbic Acid / metabolism
  • Glucose / metabolism
  • Hydrogen-Ion Concentration
  • Lung / metabolism
  • Molecular Sequence Data
  • Muscle, Skeletal / metabolism
  • Organic Anion Transporters, Sodium-Dependent / metabolism
  • Phosphorylation
  • Phylogeny
  • Protein Isoforms
  • Protein Kinase C / metabolism
  • Protein Structure, Tertiary
  • Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Sodium / metabolism
  • Sodium-Coupled Vitamin C Transporters
  • Symporters*
  • Time Factors
  • Tissue Distribution
  • Xenopus


  • Cations
  • Organic Anion Transporters, Sodium-Dependent
  • Protein Isoforms
  • Proteins
  • SLC23A1 protein, human
  • SLC23A2 protein, human
  • Sodium-Coupled Vitamin C Transporters
  • Symporters
  • Sodium
  • Protein Kinase C
  • Glucose
  • Ascorbic Acid
  • Dehydroascorbic Acid