A new phospholipase A2 isolated from the sea anemone Urticina crassicornis - Its primary structure and phylogenetic classification

FEBS Journal (Impact Factor: 4). 05/2010; 277(12):2641 - 2653. DOI: 10.1111/j.1742-4658.2010.07674.x
Source: PubMed


Disulfide pairings and active site residues are highly conserved in secretory phospholipases A2 (PLA2s). However, secretory PLA2s of marine invertebrates display some distinctive structural features. In this study, we report the isolation and characterization of a PLA2 from the northern Pacific sea anemone, Urticina crassicornis (UcPLA2), containing a C27N substitution and a truncated C-terminal sequence. This novel cnidarian PLA2 shares about 60% identity and almost 70% homology with two putative PLA2s identified in the starlet sea anemone (Nematostella vectensis) genome project. UcPLA2 lacks hemolytic and neurotoxic activities. A search of available sequences revealed that Asn27-‘type’ PLA2s are present in a few other marine animal species, including some vertebrates. The possibility that the C27N replacement represents a structural adaptation for PLA2 digestion/activity in the marine environment was not supported by experiments testing the influence of ionic strength on UcPLA2 enzymatic activity. Because of the highly divergent sequences among invertebrate group I PLA2s, it is currently not possible to identify orthologous relationships. As the Asn27-containing PLA2s are scattered among the other invertebrate group I PLA2s, they do not constitute a new, monophyletic PLA2 clade.

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