The reversible facilitated diffusion of fructose, galactose, and glucose from the cytosol to the extracellular space is mediated by tetrameric SLC2A2 (also known as GLUT2) transporter in the plasma membrane. In the epithelial cells of the small intestine, the basolateral localization of SLC2A2 (Thorens et al. 1990) enables hexose sugars derived from the diet and taken up by the action of the SLC5A1 (SGLT1) and SLC2A5 (GLUT5) transporters to be released into the circulation. The specificity of the SLC2A2 transporter has been established directly through biochemical assays of purified recombinant proteins (Colville et al. 1993; Wu et al. 1998) and indirectly through studies of patients deficient in SLC2A2 transporter protein (Santer et al. 1997).