ANOMERIC PREFERENCE OF GLUCOSE-UTILIZATION IN HUMAN ERYTHROCYTES LOADED WITH GLUCOKINASE

Human crythrocytes were loaded with homogeneous rat liver glucokinase by an encapsulation method based on hypotonic hemolysis and isotonic resealing. As assayed at 10 mM glucose, glucokinase and hexokinase activities in glucokinase-loaded crythrocytes were 218 and 384 nmol/min/gHb, respectively; whereas hexokinase activity in both intact and unloaded red cells, which contain no glucokinase activity, was about 400 nmol/min/gHb. No difference in the rate of lactate production from glucose anomers between intact and unloaded erythrocytes suggested that the encapsulation procedure itself did not affect glucose utilization in red cells. Alpha-anomeric preference in lactate production from glucose was observed in glucokinase-loaded erythrocytes, whereas the β anomer of glucose was more rapidly utilized than the α anomer in intact and unloaded crythrocytes. The results indicate that the step of glucose phosphorylation determines the anomeric preference in glucose utilization by human erythrocytes, since glucokinase and hexokinase are α- and β-preferential, respectively, in glucose phosphorylation. © 1990 Academic Press, Inc.