Two alternative pathways for docosahexaenoic acid (DHA, 22:6n-3) biosynthesis are widespread among teleost fish.

ABSTRACT: Docosahexaenoic acid (DHA) plays important physiological roles in vertebrates. Studies in rats and rainbow trout confirmed that DHA biosynthesis proceeds through the so-called "Sprecher pathway", a biosynthetic process requiring a ?6 desaturation of 24:5n-3 to 24:6n-3. Alternatively, some teleosts possess fatty acyl desaturases 2 (Fads2) that enable them to biosynthesis DHA through a more direct route termed the "?4 pathway". In order to elucidate the prevalence of both pathways among teleosts, we investigated the ?6 ability towards C24 substrates of Fads2 from fish with different evolutionary and ecological backgrounds. Subsequently, we retrieved public databases to identify Fads2 containing the YXXN domain responsible for the ?4 desaturase function, and consequently enabling these species to operate the ?4 pathway. We demonstrated that, with the exception of ?4 desaturases, fish Fads2 have the ability to operate as ?6 desaturases towards C24 PUFA enabling them to synthesise DHA through the Sprecher pathway. Nevertheless, the ?4 pathway represents an alternative route in some teleosts and we identified the presence of putative ?4 Fads2 in a further 11 species and confirmed the function as ?4 desaturases of Fads2 from medaka and Nile tilapia. Our results demonstrated that two alternative pathways for DHA biosynthesis exist in teleosts.

SUBMITTER: Oboh A 

PROVIDER: S-EPMC5478668 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature