Molecular homology of coexpressed eye‐ and liver‐specific lactate dehydrogenase isozymes from the basketmouth cichlid assessed by oxamate‐Sepharose and blue dextran‐Sepharose affinity chromatography

Abstract

AbstractRecently, several teleost fishes (Perciformes, Cichlidae) have been found that coexpress both a cathodal, liver‐specific and an anodal, eye‐specific lactate dehydrogenase (LDH), and evidence supporting the hypothesis that these are the products of two distinct genes has been presented (Holt and Leibel, '87). In this study, the molecular homology of these two isozymes from the basketmouth cichlid, Acaronia nassa, relative to each other and to eye‐specific and liver‐specific isozymes from a variety of other fishes is assessed by oxamate‐Sepharose and blue dextran‐Sepharose affinity chromatography. Whereas the eye‐specific isozyme from the basketmouth cichlid and all other LDHs from a variety of vertebrates bound tightly to the oxamate column in the presence of the cofactor NADH, the liver‐specific isozyme from basketmouth, and the testes‐specific LDH‐X from rat failed to bind. Similarly, the liver‐specific isozyme from basketmouth failed to bind to the blue dextran column, whereas the liver‐specific C4 from goldfish (Cypriniformes) bound and eluted with NADH; the eye‐specific C4 from three cichlids, including the basketmouth, and rat testis‐specific LDH‐X bound and eluted with NAD+. These results suggest that the eye‐ and liver‐specific LDH isozymes from the basketmouth cichlid are not encoded by the same locus and that this liver‐specific isozyme is very different from analogous isozymes that occur in various Cypriniform and Gadiform fishes.