Drosophila lactate dehydrogenase. Functional and evolutionary aspects

The functional characteristics of homogeneously purified LDH were studied in the eight D. melanogaster species subgroup at two different growing temperatures (14 degrees C, 25 degrees C). The Vmax, kcat, Vmax/KeNAD.KmLac and Kcat/KsNAD KmLac values detected at the permissive growing temperature of 25 degrees C, were found to converge with the consensus phylogeny of these species which consists of two (melanogaster, yakuba) complexes. This scheme, also verified by the Micro-Complement Fixation (MC'F) method in another study in our Laboratory, substantiates the connection between the enzyme function and the phylogeny of these species. We propose that the major variation of the Ldh gene in this subgroup has arisen prior to the first species divergence, the final result of which is the eight sibling species. On the other hand, the variable catalytic differentiation observed at the restrictive temperature of 14 degrees C may enrich the species with hidden adaptive possibilities.