LDH isozymes in amazon fish—III. Distribution patterns and functional properties in Serrasalmidae (Teleostei: Ostariophysi)

Abstract

1. 1. The patterns of distribution of LDH isozymes in five tissues from 12 Serrasalmidae species have been studied through two-fold serial dilution (Klebe's test) as well as the pyruvate inhibition of LDH enzyme in skeletal and heart muscles (low/high ratios). 2. 2. The species' electrophoretic patterns differ by orthologous A 4 isozyme mobilities since the orthologous B 4 isozymes present similar electrophoretic migration. These differences between Ldh-A and Ldh-B products reflect three-, four-, and five-banded patterns. Thus, different LDH isozyme numbers formed from A and B subunits should not be used as an evolutionary or phylogenetic characteristic from different taxonomic groups. 3. 3. Out of 66 pairs of species only five pairs showed significant differences in the distribution patterns in all five analyzed tissues, while no pair of species showed the same distribution in these tissues. This variation was explained as differential regulation of structural genes among tissues and/or species. 4. 4. Functional properties showed significant between the LDHs from heart and skeletal muscles, and are consistent with a preference for aerobic metabolism. We suppose that by selecting B-like subunits these fishes are able to maintain good control of aerobic/anaerobic transitions, maintaining predominantly oxidative metabolism even in hypoxic waters, with which they have to cope.