Red cell enzyme activities and properties of mutant pyruvate kinase after long-term storage of red cells in liquid nitrogen.

After 8 months of storage of normal red cells in liquid nitrogen, red cell enzyme activities were essentially unchanged, except for triose phosphate isomerase which was reduced by about half. Mutant pyruvate kinase (PK), PK Tokyo I, showed no changes in kinetic or electrophoretic properties after 8 months of storage. These findings indicate that red cells stored for a long term in liquid nitrogen can still be used for the study of mutant PK.