Properties of Adaptive Hexokinase Isozymes of the Rat1

Abstract
Rat liver hexokinase IV splits into 2 bands, designated IVf (fast) and IVa (slow) when EDTA is omitted from the starch gel electrophoresis system. The IVf disappears in diabetes whereas IVa is still present. The fast form also decreases in fasting and reappears after refeeding. Rat epididymal adipose tissue contains 2 hexokinases corresponding to I and II of rat liver. Both hexokinases of adipose tissue drop after 48 hr of fasting and return to normal after 24 hr of refeeding; this recovery does not occur in rats given puromycin or cycloheximide, 2 inhibitors of protein synthesis. The restoration of hexokinase activity produced by addition of insulin in vitro to adipose tissue from fasting rats is likewise blocked by cycloheximide, and by actinomycin D, an inhibitor of some types of RNA synthesis. Total adipose hexokinase activity fell more than 50% 3 days after induction of alloxan diabetes, recovered to normal 24 hr after insulin administration, and was 50% greater than normal after 48 hr. The changes in hexokinase II with diabetes are greater than for I. (Endocrinology81: 1397, 1967)