Adaptative features of enzymes from family sciaenidae--II. Studies on phosphoglucose isomerase (PGI) of fishes from the south coast of Uruguay.

1. The electrokinetic and thermostability properties of phosphoglucose isomerase (PGI) in three species of temperate fishes (Perciformes, Acanthopterygii)--Cynoscion striatus, Macrodon ancylodon and Micropogonias furnieri--have been analyzed in order to study the adaptative 2. Unlike most diploid fishes the PGI of these species seemed to be encoded by three PGI loci. 3. The subunits encoded by these loci occurred at different levels in the different tissues and organs analyzed. 4. Genetic variants at two loci (Pgi-A and Pgi-B2) were detected in Cynoscion striatus, and at one (Pgi-A) in Micropogonias furnieri. 5. The product of these loci could be separated in three PGI regions based on their electrophoretic distribution and thermostability properties. 6. The more anodal region (including isozymes and allozymes) was more thermolabile than the less anodal one, which is predominant in a single tissue skeletal muscle. 7. Relative activities of PGI isozymes were compared by Klebe's method to determine pattern of divergence of duplicated gene expression in the three species studied.