Lactate dehydrogenase, alanopine dehydrogenase and octopine dehydrogenase from the heart of Concholepas concholepas (Gastropoda: Muricidae)

Alanopine dehydrogenase, octopine dehydrogenase and lactate dehydrogenase activities were detected in the heart of C. concholepas. As determined by gel filtration on Sephadex G-100, the molecular weights (M_r) were 85,000, 42,000 and 52,000 for lactate dehydrogenase, alanopine dehydrogenase and octopine dehydrogenase, respectively. Substrate inhibition of the opine dehydrogenases was observed at high concentrations of both pyruvate and the corresponding amino acid (alanine or arginine). Moderate substrate inhibition of lactate dehydrogenase by pyruvate was observed; K_m values for lactate and NAD⁺ were unusually high. Alanoonine dehydrogenase was very specific for alanine and glycine was not a substrate for this enzyme. In addition to arginine, lysine was also a substrate for octopine dehydrogenase. Possible functions of the pyruvate reductases are discussed in connection with adaptation to anoxia and other regulatory processes in the heart of C. concholepas.