A comparative study of octopine dehydrogenase isoenzymes in gastropod, bivalve and cephalopod molluscs

Abstract

Abstract 1. 1. Activities of octopine dehydrogenase (ODH) and lactate dehydrogenase (LDH) were assayed in the muscular and non-muscular tissues of one gastropod (Baccinum undatum), three bivalves (Mytilus edulis, Cardium tuberculatum, Pecten jacobaeus) and one cephalopod (Loligo vulgaris) mollusc. 2. 2. In the gastropod and bivalve molluscs two bands always stained for ODH activity after polyacrylamide electrophoresis; no electrophoretic differences were found between different tissues of the same species. Furthermore, the kinetic properties of purified ODH from M. edulis and B. undatum showed no essential differences between tissues of the same species. The data suggest that octopine formation and re-oxidation could take place without the need for transportation between tissues. 3. 3. Preparation of ODH from the optic lobe and mantle tissue of L. vulgaris differ in elution behavior on Blue Sepharose and in electrophoretic mobility. 4. 4. Kinetic studies suggest that optic lobe ODH is analogous to vertebrate H-type LDH and mantle muscle ODH resembles vertebrate muscle-type LDH; for example, optic lobe ODH is strongly substrate inhibited by pyruvate and octopine and more product (octopine) inhibited than the muscle form. Optic lobe ODH forms an inhibitory quaternary complex (enzyme-pyruvate-arginine-NAD+), analogous to the abortive ternary complex of H-type LDH. Finally, the optic lobe ODH has a higher affinity for octopine and NAD+ than muscle ODH. 5. 5. Increased levels of octopine in the mantle muscle, blood and optic lobe after exhaustive swimming and hypoxic recovery support the view that octopine is produced in the mantle via the reaction of the muscle isoenzyme and is subsequently flushed out into the blood and transported to other tissues, such as the optic lobe, for re-oxidation via the optic lobe isoenzyme.