Galactokinase activity and red blood cell age

Human erythrocyte galactokinase has been studied during red cell aging. The decay rate of enzyme activity is slower than glucose-6-phosphate dehydrogenase which is used as red cell age marker. The Michaelis constants for galactose and ATPMg²⁻ of galactokinase of young cells are similar to the Km’s of the enzyme of total cells, while the Km increases in old cells. The behaviour of galactokinase during cell aging is similar to that of other erythrocyte enzymes.