Meeting Abstract
Ctenophores have taken on new importance in revealing animal origins with modern work showing their position near the root of the metazoan tree, but an increased interest in this understudied group has also revealed new mysteries. Notably, ctenophore tyrosine metabolism is peculiar: the group lacks the conserved enzymatic machinery to produce catecholamine neurotransmitters from tyrosine and the gene for tyrosyl tRNA ligase is missing. We show evidence both for the presence of tyrosine metabolites and for their functions in several contexts in ctenophores, plausible given that the ctenophore genome encodes uncharacterized tyrosinases. First, the colloblast adhesive of tentacular ctenophores may be L-DOPA based, similar to mussel byssus. We also found immunohistochemical evidence suggesting DOPA’s presence in the subepithelial nerve net. We also examined Beroid ctenophores and found evidence of tyrosine metabolites in the epithelial pigments via UV-Vis, Raman, FTIR, and EPR spectroscopy. Taken together, these findings suggest that ctenophores have the ability to metabolize tyrosine into useful o-diphenol and o-quinone derivatives such as DOPA and dopachrome independent of the dopamine biosynthetic pathway, and use them in a variety of biochemical and physiological contexts. We show that ctenophores’ noncanonical use of DOPA may shed light on the origins of neurological DOPA signaling in the rest of metazoans.
