ANALYSIS OF CATALYTIC ACTION OF TRANSGLUTAMINASE INDUCED IN HUMAN PROMYELOCYTIC LEUKEMIA (HL-60) AND HUMAN HEPATOBLASTOMA (HEPG2) CELLS

Transglutaminase is a calcium-dependent enzyme that catalyzes an amine incorporation and a cross-linking of proteins, Intracellular transglu taminase is induced when human promyelocytic leukemia HL-60 cells are treated with retinoic acid and human hepatoblastoma HEpG2 cells, with interleukin-6. To find whether the intracellular reaction catalyzed by transglutaminase increases when the enzyme is induced in these cells, the transglutaminase-catalyzed incorportation of C-14-labeled methyla mine into cellular proteins was measured, The incorporation level of t he labeled methylamine into proteins of HL-60 and HepG2 cells did not increase after the transglutaminase had been induced, The presence of the calcium ionophore A23187 did not affect these results, These findi ngs suggested that even after the enzyme induction the catalytic actio n of intracellular transglutaminase is maintained at a constant level in these cells by unknown regulatory mechanism(s).