De gereduceerde vorm wordt met SCVT1/2 als transporteiwit door het darmepitheel opgenomen.
De geoxideerde vorm wordt met (GLUT1,3 en 4) getransporteerd.
Uit wikipedia: SVCT1 and SVCT2 imported the reduced form of ascorbate across plasma membrane.
Uit het artikel waarnaar in wiki wordt verwezen.
Independently from their biosynthetic ability, all animalcells are strictly dependent on the presence of functional vitamin C transporters, which determine the distribution of this molecule between extra- and intra-cellular fluids.
Both the reduced (ascorbic acid) and the oxidised (dehydroascorbic acid) forms of vitamin C can be transported across the plasma membrane, although by distinct carriers.
Dehydroascorbic acid can be internalized by facilitative hexose transporters (GLUT1, GLUT3 and GLUT4)(Rumsey et al., 1997, 2000) and then reduced to ascorbic acid by different enzymatic systems. Conversely, the reduced
form is imported by an active mechanism, requiring two sodium-dependent vitamin C transporters (SVCT1 and SVCT2), cloned for the first time in 1999 (Tsukaguchi
et al., 1999).
SVCT1 and SVCT2 belong to a family of nucleobase transporters, which includes Aspergillus nidulans uric acidxanthine permease A (UapA) and general purine permease (UapC), bacterial xanthine transporter (PbuX), uracil transporter (UraA) and membrane-bound uracil permease (PyrP) (Faaland et al., 1998; Meintanis et al., 2000).
These two proteins have no structural homology with any other mammalian membrane transporter. In humans, the family of ascorbate transporters includes SVCT1 (previously identified as yolk-sac permease-like molecule 3, YSPL3) and SVCT2 (yolk-sac permease-like molecule 2, YSPL2, or KIAA0238) and two orphan members, named SVCT3 (yolk-sac permease-like molecule 1, YSPL1) and SVCT4 (Takanaga et al., 2004). Characterization of SVCT1 and SVCT2 indicates that they have a high sequence homology; nonetheless they exert distinct functions, depending on their cellular distribution.
Bron: Savini, I., Rossi, A., Pierro, C., et al. SVCT1 and SVCT2: key proteins for vitamin C uptake. Amino Acids 2008; 34: 347-355
Veranderd door Gerard, 26 januari 2010 - 12:48