An examination of the age-related patterns of decay of the hexokinases of human red cells.

A previous method for red cell fractionation by density gradient centrifugation, using a swing-out rotor, has been scaled up to deal with larger volumes of red cells. This method, involving the use of a zonal rotor, is described and has been applied to the study of the decay of hexokinase in the red cells of normal individuals. Hexokinase activity was seen to fall very rapidly in the young cells followed by a much more gradual decline in older cells. It is estimated that the mature red cell probably contains no more than 2-3% of the hexokinase activity originally present in the reticulocyte. An electrophoretic study showed a changing pattern of the isozymes HK1 and HK2 with increasing cell age. HK2 declines very rapidly in the early fractions whereas HK1 appears to decay more gradually.