The Properties and Functions of Alanopine Dehydogenase and Octopine Dehydrogenase from the Pedal Retractor Muscle of Strombidae (Class Gastropoda)

Abstract

The pedal retractor muscles of Strombidae contain high activities of both alanopine dehydrogenase and octopine dehydrogenase, raising questions as to the functions of these two enzymes during muscle anoxia associated with locomotion. Alanopine dehydrogenase and octopine dehydrogenase were isolated from the pedal retractor muscle of Strombus luhuanus, and their structural and kinetic properties investigated. Alanopine dehydrogenase occurs as a single electrophoretic form with a molecular weight of approx. 42,000. Octopine dehydrogenase was electrophoretically polymorphic, existing as three alleles in the population of animals studied. The major form of the enzyme had a molecular weight of approx. 39,000. Both enzymes displayed similar pH optima for the forward (pyruvate reduction) reaction and similar Km values for the common substrates pyruvate and NADH. During bursts of leaping, both octopine and strombine/alanopine accumulated in the pedal retractor muscles of Strombidae. However, during recovery from exercise, only strombine/alanopine accumulated. Octopine was a potent inhibitor of the forward reaction catalyzed by octopine dehydrogenase, and may act to prevent further octopine production during the recovery phase. The results of this study show that both alanopine dehydrogenase and octopine dehydrogenase are functioning to catalyze the terminal step of anaerobic glycolysis during muscle anoxia associated with locomotion.