Control of glycolysis in vertebrate skeletal muscle during exercise.
The gastrocnemius muscle of the frog (Rana temporaria) has a high capacity for anaerobic glycolysis from glycogen. Glycolytic metabolites and effectors of phosphofructokinase, particularly the hexose bisphosphates, were followed in muscle during exercise (swimming between 5 s and 5 min), recovery (rest for up to 2 h after 5 min of swimming), and repeated exercise (swimming for up to 60 s after 2 h of recovery). Glycogen phosphorylase and phosphofructokinase were swiftly activated with exercise. The hexose bisphosphates followed markedly different time courses. Fructose 1,6-bisphosphate was transiently increased in both exercise and repeated exercise. This appears to be an effect rather than a cause of phosphofructokinase activation. Glucose 1,6-biphosphate was accumulated only while phosphofructokinase was active and was unchanged at other times. Fructose 2,6-biphosphate showed a 10-fold transient increase on exercise in rested frogs, almost disappeared from the muscle during recovery, and did not change during repeated exercise. Fructose 2,6-biphosphate is a potent activator of phosphofructokinase in vitro under near physiological assay conditions, and it may serve this function also in vivo during exercise. Glucose 1,6-biphosphate could be an activator of phosphofructokinase in repeated exercise when fructose 2,6-biphosphate is not available.
Krause
U
U
Institut für Zoologie, Johannes Gutenberg-Universität, Mainz, Germany.
Wegener
G
G
D000818:Animals; D004789:Enzyme Activation; D006003:Glycogen / Q000378:metabolism; D006019:Glycolysis; D006600:Hexosephosphates / Q000494:pharmacology; D006614:Hindlimb; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010732:Phosphofructokinase-1 / Q000378:metabolism; D005082:Physical Exertion; D011896:Rana temporaria
D006600:Hexosephosphates; D006003:Glycogen; D010732:Phosphofructokinase-1