Horseshoe crab lactate dehydrogenases: evidence for dimeric structure.

D-Lactate dehydrogenase of Limulus polyphemus occurs in six molecular forms, not in five as does the L-lactate dehydrogenase of vertebrates. The electrophoretic pattern of bands in an apparent genetic variant is incompatible with a model of tetrameric molecular structure, and suggests, rather, that the three more anodally migrating isozymes are dimer molecules, the polypeptide subunits of which are encoded by two genetic loci and are not involved in the formation of the lower triad of isozymes.