The cDNA cloning and molecular evolution of reptile and pigeon lactate dehydrogenase isozymes

The cDNAs encoding lactate dehydrogenase isozymes LDH-A (muscle) and LDH-B(heart) from alligator and turtle and LDH-A, LDH-B, and LDH-C (testis) frompigeon were cloned and sequenced. The evolutionary relationships amongvertebrate LDH isozymes were analyzed. Contrary to the traditional beliefthat the turtle lineage branched off before the divergence between thelizard/alligator and bird lineages, the turtle lineage was found to beclustered with either the alligator lineage or the alligator-bird clade,while the lizard lineage was found to have branched off before thedivergence between the alligator/turtle and bird lineages. The pigeontesticular LDH-C isozyme was evidently duplicated from LDH-B (heart), so itis not orthologous to the mammalian testicular LDH-C isozymes.