Class I transporters are able to transport D-glucose, but not D-fructose, in the direction of the concentration gradient and may be inhibited non-selectively by phloretin and cytochalasin B. GLUT1 is the major glucose transporter in brain, placenta and erythrocytes, GLUT2 is found in the pancreas, liver and kidneys, GLUT3 is neuronal and placental, while GLUT4 is the insulin-responsive transporter found in skeletal muscle, heart and adipose tissue. GLUT14 appears to result from gene duplication of GLUT3 and is expressed in the testes [3].

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2. Uldry M, Ibberson M, Hosokawa M, Thorens B. (2002) GLUT2 is a high affinity glucosamine transporter. FEBS Lett., 524 (1-3): 199-203. [PMID:12135767]

3. Wu X, Freeze HH. (2002) GLUT14, a duplicon of GLUT3, is specifically expressed in testis as alternative splice forms. Genomics, 80 (6): 553-7. [PMID:12504846]