Rabbit red blood cell hexokinase:intracellular distribution during reticulocytes maturation

The intracellular localization and isozyme distribution of hexokinase were studied during rabbit reticulocyte maturation and aging. In reticulocytes 50% of the enzyme was particulate while in the mature erythrocytes all the hexokinase activity was soluble. The bound enzyme co-sediments with mitochondria and by column chromatography it was found to be hexokinase Ia. The cytosol of reticulocytes contains hexokinase Ia (38%) and hexokinase Ib (62%) while the mature erythrocytes contain only hexokinase Ia. The amount of bound hexokinase decreases very quickly during cell maturation and aging as was shown by following in vivo reticulocyte maturation or by analysis of hexokinase compartmentation in cells of different ages, obtained by density gradient ultracentrifugations. A role for this intracellular distribution of hexokinase is suggested.