Desaturases and elongases involved in polyunsaturated fatty acid biosynthesis in aquatic invertebrates: a comprehensive review

Invertebrates represent a large proportion of the biomass in aquatic ecosystems, particularly in the ocean. In recent years, invertebrates have been well-consolidated models in evolutionary developmental biology research and, consequently, genomic and transcriptomic sequence databases from a plethora of species across the animal kingdom have become available. This has provided an excellent source of evidence confirming that invertebrates operate endogenous mechanisms for PUFA production. The present paper reviews the current knowledge of gene complement and, where possible, the function of desaturases and elongases with pivotal roles in PUFA biosynthesis of aquatic invertebrates. More specifically, this review covers three major enzyme types, namely omega x desaturases, front-end desaturases and elongases, that have been characterised from species of sponges, cnidarians, molluscs, annelids, crustaceans, rotifers, echinoderms and non-vertebrate chordates (amphioxus and sea squirt). These studies have shown that invertebrates operate alternative and unusual pathways of PUFA biosynthesis involving gene families with complex phylogeny and functional diversity. Consequently, research in this area provides potentially valuable molecular tools in the form of genes that can be used in the biotechnological production of n-3 products.