Diversity and evolution of tyrosinase enzymes involved in the adhesive systems of mussels and tubeworms

Mussels and tubeworms have evolved similar adhesive systems to cope with the hydrodynamics of intertidal environments. Both secrete adhesive proteins rich in DOPA, a post-translationally modified amino acid playing essential roles in their permanent adhesion. DOPA is produced by the hydroxylation of tyrosine residues by tyrosinase enzymes, which can also oxidize it further into dopaquinone. We have compiled a catalog of the tyrosinases potentially involved in the adhesive systems of <i>Mytilus edulis</i> and <i>Sabellaria alveolata</i>. Some were shown to be expressed in the adhesive glands, with a high gland specificity in mussels but not in tubeworms. The diversity of tyrosinases identified in the two species suggests the coexistence of different enzymatic activities and substrate specificities. However, the exact role of the different enzymes needs to be further investigated. Phylogenetic analyses support the hypothesis of independent expansions and parallel evolution of tyrosinases involved in DOPA-based adhesion in both lineages.