Regulation of Hexokinase Isozymes: Apparent Interconversion between Type II and Type III or Inactive Enzyme Complex Formation in Rat Tissues

抄録

The regulatory mechanism for the three low K_m hexokinase [EC 2. 7. 1. 1] isozymes was studied with carrageenin-induced proliferative granuloma tissue of rats in which hexokinase activity per g of tissue was much higher as compared with that in the liver and muscle.
The electrophorsis of hexokinase isozymes on cellulose acetate membrane revealed that the granuloma contained Types I, II and III, and their relative proportions were altered corresponding to the change in the proliferative activity of the tissue. Only Type III was detected first, which was followed by the appearance of Type I. Then, gradual replacement of Type III by Type II was observed.
Possible role of insulin in the regulation of the hexokinase isozyme pattern was examined. In the absence of mercaptoethanol (ME) and EDTA, administration of insulin caused increase in Type III and concomitant decrease in Type II in the granuloma, seemingly converting Type II to III. This change was apparenty inhibited by puromycin and actinomycin D administration. In the liver and muscle, the insulin treatment caused an almost disappearance of Type II without appreciable change in Type III. In the muscle, the change in the isozymogram was seen as early as 5 min after the insulin injection. The effects of insulin, however, were not found in the presence of ME and EDTA during the preparation and analytical procedures.