Sequence of the Pearl Oyster Carbonic Anhydrase-Related Protein and Its Evolutionary Implications

Carbonic anhydrases are conserved in vertebrates and invertebrates, and a noncatalytic carbonic anhydrase-related protein VIII (CARP VIII) has been found in deuterostomes and the phylum Placozoa. I isolated a cDNA encoding a noncatalytic CARP from the mantle of the pearl oyster Pinctada fucata. The polypeptide (CARP-1) predicted from the nucleotide sequence shares 44-60% identity with known CARP VIII sequences, and its phylogenetic analysis showed that P. fucata formed a single group with deuterostome invertebrates. However, since CARP VIII sequences are not identified in protostomes, these results suggest that CARP-1 may have originated in molluscs independently from deuterostome CARP VIII sequences.