MOLECULAR EVOLUTION OF THE ALDO-KETO REDUCTASE GENE SUPERFAMILY

The aldo-keto reductase enzymes comprise a functionally diverse gene f amily which catalyze the NADPH-dependant reduction of a variety of car bonyl compounds. The protein sequences of 45 members of this family we re aligned and phylogenetic trees were deduced from this alignment usi ng the neighbor-joining and Fitch algorithms. The branching order of t hese trees indicates that the vertebrate enzymes cluster in three grou ps, which have a monophyletic origin distinct from the bacterial, plan t, and invertebrate enzymes. A high level of conservation was observed between the vertebrate hydroxysteroid dehydrogenase enzymes, prostagl andin F synthase, and p-crystallin of Xenopus laevis. We infer from th e phylogenetic analysis that prostaglandin F synthase may represent a recent recruit to the eicosanoid biosynthetic pathway from the hydroxy steroid dehydrogenase pathway and furthermore that, in the context of gene recruitment, Xenopus laevis p-crystallin may represent a shared g ene.