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 ms 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. ∼17–20 mM). Glucosamine transport by GLUT2 was confirmed in mammalian cells and, using hepatocytes from control or GLUT2-null mice, HgCl 2-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.