Modification of the glyoxalase system in human HL60 promyelocytic leukaemia cells during differentiation to neutrophils in vitro.

The glyoxalase system of human promyelocytic leukaemia HL60 cells was substantially modified during differentiation to neutrophils. The activity of glyoxalase I was decreased and the activity of glyoxalase II was markedly increased relative to the level in control HL60 promyelocytes. There was a decrease in the apparent maximum velocity, Vmax, of glyoxalase I, and an increase in the Vmax of glyoxalase II. The apparent Michaelis constants for both enzymes remained unchanged. The flux of intermediates metabolised via the glyoxalase system increased during differentiation, as judged by the formation of D-lactic acid, whereas the percentage of glucotriose metabolised via the glyoxalase system remained unchanged. The cellular concentrations of the glyoxalase substrates, methylglyoxal and S-D-lactoylglutathione, were markedly decreased during differentiation. The maturation of HL60 promyelocytes is associated with an increased ability to metabolise S-D-lactoylglutathione by glyoxalase II and a concomitant decrease in the mean intracellular concentrations of S-D-lactoylglutathione and methylglyoxal. The maintenance of a high concentration of S-D-lactoylglutathione in HL60 promyelocytes may be related to the status of the microtubular cytoskeleton, since S-D-lactoylglutathione potentiates the GTP-promoted assembly of microtubules.