Isolation and characterization of two molecular forms of octopine dehydrogenase from Pecten maximus L

Two forms, A and B, of octopine dehydrogenase from Pecten muximus L. straited adductor muscles were separated by ion-exchange chromatography and purified to homogeneity. Their kinetic properties were similar and, among others, the mnemonical behaviour, previously found for octopine dehydrogenase, was confirmed. Structural features, determined by polyacrylamide gel electrophoresis with and without sodium dodecylsulfate, amino acid composition, immunological tests and heat stability were compared. The only differences between the two forms are their charge and their sensibility to various chemical treatments. Assays of reciprocal conversion of the two forms by oxidation, reduction or deamidation failed. No tissue specificity and no relation to any physiological conditions could be observed. However, a constant ratio A:B = 1:4 was statistically found in crude extracts as well as in the purified enzyme. It therefore seems possible to assume that the two forms of octopine dehydrogenase pre-exist in living P. maximus, although their genetic origin has to be established.