ENHANCED CATALYTIC ACTIVITY OF HEXOKINASE BY WORK-INDUCED MITOCHONDRIAL BINDING IN FAST-TWITCH MUSCLE OF RAT

Using a teased muscle fiber preparation, we determined the activity of mitochondrially bound hexokinase in rat fast-twitch muscle under cont rol conditions and after low-frequency stimulation periods for up to 2 h. As compared to soluble hexokinase, mitochondrial binding led to st imulation of glucose 6-phosphate production. Low-frequency stimulation greatly enhanced glucose 6-phosphate formation which was 100% and 250 % elevated after 1 and 2 h, respectively, These observations point to a mechanism which rapidly increases the catalytic activity of hexokina se through binding to the mitochondrial surface. (C) 1997 Federation o f European Biochemical Societies.