Glucose Metabolism in Normal Erythrocytes II Factors Influencing the Hexokinase Step

Factors influencing the rate of glucose conversion in red blood cells have been investigated using haemolysates and a purified hexokinase system. The KM‐values for glucose and ATP indicate that the glucose concentrations usually occurring in red blood cells are optimal, whereas variations around the physiological ATP‐concentration will strongly influence the conversion rate. Glucose 6‐phosphate is a potent competitive inhibitor of hexokinase with respect to ATP. Other phosphocompounds tested, fructose 6‐phosphate, fructose 1,6‐diphosphate and 2,3‐diphosphoglycerate, have no inhibitory effect. Inorganic phosphate decreases the inhibition caused by glucose 6‐phosphate. The mechanism for this action is not clear; an interpretation of the data obtained is suggested, however. In intact red blood cells, inosine blocks the phosphorylation of glucosee. The explanation for this effect appears to be the marked increase in glucose 6‐phosphate and the decrease in inorganic phosphate.