No co-expression of LDH-C in amazon cichlids

Abstract

As commonly found among other advanced telcosts, lactate dehydrogenase (LDH, EC. 1.1.1.27) from cichlid fish exhibits the eye-specific LDH-C4 isozyme. In the last few yeats, some authors have described the co-expression of a distinct liver-specific form in addition to the eye-specific LDH isozymes in cichlid fish. Because liver-specific isozymes have been described before in Gadiformes as the product of the same LDH-C*locus, such. co- expression of these isozymes was explained as the result of a fourth locus for LDH. Our studies on Amazon cichlid fishes revealed that the specific isozyme present in liver is the result of activity of another enzyme: alcohol dehydrogenase (ADH, EC. 1.I.1.1.). Several tests with ADH specific staining and the use of ADH inhibitors confirmed that the isozyme described as LDH in liver of Acaron/a nassa is actually the result of ADH activity. It is common during the staining procedure for LDH and other dehydrogenases such as malate dehydrogenase (EC. 1.1.1.37) for the ADH isozyme to also appear. Considering these results, we suggest that LDH occurs as the product of three loci (LDH- A* LDH-B* and LDH-C*) in these fish.