Phylogenetic comparison of opine dehydrogenase sequences from marine invertebrates

Three cDNA sequences encoding putative opine dehydrogenase (OpDH) enzymes from the mussel Mytilus galloprovincialis were obtained. The deduced amino acid sequences were clearly distinguishable from each other, showing that several OpDH transcripts could occur in the mussel tissues (p distance 0.46-0.55). When these sequences were aligned and compared with published databank proteins, the range of identity among the M. galloprovincialis OpDH and the strombine dehydrogenase from Ostrea edulis was 51-59 %, the best hit in the three comparisons, followed by OpDH enzymes from other marine invertebrates. Sequence alignment revealed structural motifs possibly related to the binding sites of the substrates. A phylogenetic analysis compared M. galloprovincialis OpDH and annotated sequences belonging to five phyla and seven taxonomic classes, including 19 species, representing the five OpDH protein family members. The phylogenetic tree clustered the OpDH enzymes according to the evolutionary relationships of the species and not to the biochemical reaction catalyzed.