GLUT2 is a high affinity glucosamine transporter

When expressed in Xenopus oocytes, GLUT1, 2 and 4 transport glucosamine with V-max values that are three- to four-fold lower than for glucose. The K(m)s for glucosamine and glucose of GLUT1 and GLUT4 were similar. In contrast, GLUT2 had a much higher apparent affinity for glucosamine than for glucose (K-m = 0.8 +/- 0.1 mM vs. similar to17-20 mM). Glucosamine transport by GLUT2 was confirmed in mammalian cells and, using hepatocytes from control or GLUT2-null mice, HgCl2-inhibitable glucosamine uptake by liver was shown to be exclusively through GLUT2. These data have implications for glucosamine effects on impaired glucose metabolism and for structure-function studies of transporter sugar binding sites. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.