GLUT family

Joost H-G, Thorens B (2001) The extended GLUT-family of sugar/polyol transport facilitators - nomenclature, sequence characteristics, and potential function of its novel members. Mol MembrBiol 18 247-256... 

In contrast to GLUT1-GLUT4, which all transport glucose at physiological concentrations, GLUT5 transports fructose. The properties of other members of the GLUT family have not yet been studied in detail. 

Fructose both enters and leaves absorptive epithelial cells by facilitated diffusion, apparently via transport proteins that are part of the GLUT family. The transporter on the luminal side has been identified as GLUT 5. Although this transporter can transport glucose, it has a much higher activity with fructose (see Fig. 27.12). Other fructose transport proteins also may be present. For reasons as yet unknown, fructose is absorbed at a much more rapid rate when it is ingested as sucrose than when it is ingested as a monosaccharide. 

The genes of the growing number of members of both the SGLT and the GLUT family have been identified during recent years. This was a key step in the study of the function of these proteins, of their tissue-specific expression and in the identification of genetic defects. 

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