Hemin-induced conversion of pyruvate kinase isozymes in K562 cells

The effects of hemin on the conversion of pyruvate kinase (PK) isozymes from the M2-type to the L-type in K562 cells were investigated. Immunofluorescence, ion exchange chromatography, and electrophoretic studies showed that the untreated K562 cells contained only the M2-type PK, while eight to 20 days after induction with hemin, concomitant with hemoglobin F synthesis, L-type PK levels increased while M2-type PK levels decreased. Electrophoretic study revealed three hybrid isozymes of the L-type and M2-type PK. We conclude that the conversion of PK isozymes from the M2-type to the L-type in erythroid precursor cells occurs in the early stage of maturation.