Although erythrocytes readily metabolize fructose, it has not been kno
wn how this sugar gains entry to the red blood cell. We present eviden
ce indicating that human erythrocytes express the fructose transporter
GLUT5, which is the major means for transporting fructose into the ce
ll. Immunoblotting and immunolocalization experiments identified the p
resence of GLUT1 and GLUT5 as the main facilitative hexose transporter
s expressed in human erythrocytes, with GLUT2 present in lower amounts
. Functional studies allowed the identification of two transporters wi
th different kinetic properties involved in the transport of fructose
in human erythrocytes. The predominant transporter (GLUT5) showed an a
pparent Km for fructose of approximately 10 mmol/L. Transport of low c
oncentrations of fructose was not affected by 2-deoxy-D-glucose, a glu
cose analog that is transported by GLUT1 and GLUT2. Similarly, cytocha
lasin B, a potent inhibitor of the functional activity of GLUT1 and GL
UT2, did not affect the transport of fructose in human erythrocytes. T
he functional properties of the fructose transporter present in human
erythrocytes are consistent with a central role for GLUT5 as the physi
ological transporter of fructose in these cells. (C) 1997 by The Ameri
can Society of Hematology.