The GLUT protein family is encoded by SLC2 genes and is a member of the major facilitator superfamily of membrane transporters. The GLUT proteins contain 12 membrane-spanning domains, an N-linked glycosylation site, and intracellular NH₂ and COOH termini, in addition to several conserved residues and motifs designated “sugar transporter signatures”.

Fourteen GLUT isoforms have been identified and divided into 3 different group classes based on sequence similarity and structural and functional characteristics. GLUT2 together with GLUT 1,3,4 and 14 belongs to Class I group¹.

GLUT2 acts as a facilitative glucose transporter in the liver, pancreas, intestine, kidney, and brain and is able to process high sugar concentrations. Due to the transporter’s low affinity and high capacity, it guaranties large bidirectional fluxes of glucose in and out of the cell. GLUT2 also can transport other dietary sugars including fructose and galactose, when they are present in physiological concentrations².

GLUT2 mutations cause a severe and rare syndrome called Fanconi-Bickel, an autosomal recessive disorder in carbohydrate metabolism. Patients with Fanconi-Bickel disorder suffer from hepatomegaly, nephropathy, fasting hypoglycemia, sugar intolerance, and growth retardation. In addition, a GLUT2 polymorphism has been associated with preferences for sugary food².