INFLUENCE OF EXERCISE ON THE DISTRIBUTION OF ENZYMES IN TROUT WHITE MUSCLE AND KINETIC-PROPERTIES OF AMP-DEAMINASE FROM FREE AND BOUND FRACTIONS

Effects of exercise on the distribution of phosphofructokinase (PFK), fructose-1,6-biphosphatase (FBPase), and AMP-deaminase between free an d particulate-bound fractions was analyzed in white skeletal muscle of rainbow trout Oncorhynchus mykiss. With a widely used technique for t he separation of free and bound enzyme fractions (homogenization in lo w ionic strength, high sucrose buffer), the data showed that the amoun t of bound PFK increased from 64 to 95% during burst swimming whereas other enzymes were unaffected. Since this data for AMP-deaminase contr asted with earlier reports, different methods of separating free and b ound enzyme were evaluated. A clear effect of exercise on AMP-deaminas e binding occurred when high ionic strength media (either KCl or KF) w ere used; in extraction media containing 150 mM KCl, the percent bound rose from 30% in controls to 97% after 1 min burst swimming. Exercise also produced stable changes to AMP-deaminase kinetic properties, inc luding for the bound enzyme (compared with the free) a 2-fold higher K -m AMP, a 3-fold higher K-i for inorganic phosphate, and a 60% increas e in K-a ADP after 1 min burst exercise. The data suggest that AMP-dea minase in working skeletal muscle is subject to combined controls by a llosteric effecters, post-translational modification, and distribution between free and bound states.