[Characteristics of functioning of succinate dehydrogenase from flight muscles of the bumblebee Bombus terrestris (L.)].

It was found that the succinate oxidation rate in mitochondria of flight muscles of Bombus terrestris L. in- creased by a factor of 2.15 after flying for 1 h. An electrophoretically homogenous preparation of succinate dehydrogenase with a specific activity of 7.14 U/mg protein and 81.55-fold purity was isolated from B. terrestris flight muscles. It is shown that this enzyme is represented in the muscle tissue by only one isoform with R,f = 0.24. The molecular weight of the native molecule and its subunits A and B was determined. The kinetic characteristics ofsuccinate dehydrogenase (Km = 0.33 mM) and the optimal concentration of hydrogen ions (pH 7.8) were established, and the effect of salts on the enzyme activity was studied. The role of succinate as a respiratory substrate in stress and the structural and functional characteristics of the succinate dehydrogenase system in the flight muscles of insects are discussed.