Adaptative features of enzymes from family sciaenidae (Perciformes)--I. Studies on soluble malate dehydrogenase (s-MDH) and creatinine kinase (CK) of fishes from the south coast of Uruguay.

1. Electrophoretic analysis of the soluble malate dehydrogenase (s-MDH) and creatine kinase (CK) isozyme patterns of three species of temperate fishes (Scianidae, Perciformes) indicates at least two loci for s-MDH, Mdh-A and Mdh-B, and four CK, Ck-A, Ck-B, Ck-C and Ck-D. 2. The subunits encoded by these loci occurred at different levels in different tissues and organs analyzed. 3. Through electrophoretic analysis the products of these loci showed different behaviour to changes in temperature. 4. Relative activities of s-MDH and CK isozymes were compared by Klebe's (1975) method to determine pattern of divergence of duplicated gene expression in the three studied species.