Alpha- and Beta-Monosaccharide Transport in Human Erythrocytes

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology

Publication Date


Document Type



Biological Transport; Membrane Transport Proteins; Erythrocytes; Glucose Transporter Type 1


Biochemical Phenomena, Metabolism, and Nutrition | Biochemistry, Biophysics, and Structural Biology | Medical Biophysics | Medical Physiology | Pharmacology, Toxicology and Environmental Health


Equilibrative sugar uptake in human erythrocytes is characterized by a rapid phase, which equilibrates 66% of the cell water, and by a slow phase, which equilibrates 33% of the cell water. This behavior has been attributed to the preferential transport of beta-sugars by erythrocytes (Leitch JM, Carruthers A. Am J Physiol Cell Physiol 292: C974-C986, 2007). The present study tests this hypothesis. The anomer theory requires that the relative compartment sizes of rapid and slow transport phases are determined by the proportions of beta- and alpha-sugar in aqueous solution. This is observed with d-glucose and 3-O-methylglucose but not with 2-deoxy-d-glucose and d-mannose. The anomer hypothesis predicts that the slow transport phase, which represents alpha-sugar transport, is eliminated when anomerization is accelerated to generate the more rapidly transported beta-sugar. Exogenous, intracellular mutarotase accelerates anomerization but has no effect on transport. The anomer hypothesis requires that transport inhibitors inhibit rapid and slow transport phases equally. This is observed with the endofacial site inhibitor cytochalasin B but not with the exofacial site inhibitors maltose or phloretin, which inhibit only the rapid phase. Direct measurement of alpha- and beta-sugar uptake demonstrates that erythrocytes transport alpha- and beta-sugars with equal avidity. These findings refute the hypothesis that erythrocytes preferentially transport beta-sugars. We demonstrate that biphasic 3-O-methylglucose equilibrium exchange kinetics refute the simple carrier hypothesis for protein-mediated sugar transport but are compatible with a fixed-site transport mechanism regulated by intracellular ATP and cell shape.


membrane transport; erythrocytes; GLUT1

DOI of Published Version



Am J Physiol Cell Physiol. 2009 Jan;296(1):C151-61. Epub 2008 Nov 5. Link to article on publisher's site

Journal/Book/Conference Title

American journal of physiology. Cell physiology

Related Resources

Link to article in PubMed

PubMed ID