DETECTION OF AN NAD(-DEPENDENT MALIC ENZYME LOCUS IN THE ATLANTIC SALMON SALMO-SALAR AND OTHER SALMONID FISH())

Electrophoretic studies of malate oxidoreductases routinely assess var iation in two enzymes, malate dehydrogenase (EC 1.1.1.37) and malic en zyme (NADP(+)) (EC 1.1.1.40). By modification of the standard isozyme staining conditions for these enzymes, we have resolved a new NAD(+)-p referring, MgCl2-requiring malic enzyme which is indicated to be EC 1. 1.1.39. The enzyme was detected in 10 salmonid fish species of the gen era Salmo, Salvelinus, and Onchoryhncus. Phenotypic variation indicate s that the novel enzyme is tetrameric and coded by a single locus. Inh eritance in S. salar follows a single-locus model and the phenotypes a re unlinked to polymorphisms for (s)MDH-3,4 and (m)MEP-2*, two malate oxidoreductase loci previously shown to be variable in this species.