Influence of exercise on the activity and the distribution between free and bound forms of glycolytic and associated enzymes in tissues of horse mackerel

The effects of short-term burst (5 min at 1.8 m/s) swimming and longterm cr uiser (60 min at 1.2 m/s) swimming on maximal enzyme activities and enzyme distribution between free and bound states were assessed for nine glycolyti c and associated enzymes in tissues of horse mackerel, Trachurus mediterran eus ponticus. The effects of exercise were greatest in white muscle. The ac tivities of phosphofructokinase (PFK), pyruvate kinase (PK), fructose-1,6-b isphosphatase (FBPase), and phosphoglucomutase (PGM) all decreased to 47, 3 7, 37 and 67%, respectively, during 60-min exercise and all enzymes except phosphoglucoisomerase (PGI) and PGM showed a change in the extent of bindin g to subcellular particulate fractions during exercise. In red muscle, exer cise affected the activities of PGI, FBPase, PFK, and lactate dehydrogenase (LDH) and altered percent binding of only PK and LDH. In liver, exercise i ncreased the PK activity 2.3-fold and reduced PGI 1.7-fold only after 5 min of exercise but altered the percent binding of seven enzymes. Fewer effect s were seen in brain, with changes in the activities of aldolase and PGM an d in percent binding of hexokinase, PFK and PK. Changes in enzyme activitie s and in binding interactions with subcellular particulate matter appear to support the altered demands of tissue energy metabolism during exercise.