Biosynthesis of long-chain polyunsaturated fatty acids in the razor clam Sinonovacula constricta: Characterization of four fatty acyl elongases and a novel desaturase capacity

Biochim Biophys Acta Mol Cell Biol Lipids. 2019 Aug;1864(8):1083-1090. doi: 10.1016/j.bbalip.2019.04.004. Epub 2019 Apr 16.

Abstract

As an unusual economically important aquaculture species, Sinonovacula constricta possesses high levels of long-chain polyunsaturated fatty acids (LC-PUFA). Previously, our group identified fatty acyl desaturases (Fad) with Δ5 and Δ6 activities in S. constricta, which was the first report of Δ6 Fad in a marine mollusc. Here, we further successfully characterize elongases of very long-chain fatty acids (Elovl) in this important bivalve species, including one Elovl2/5, two Elovl4 isoforms (a and b) and a novel Elovl (c) with Elovl4 activity. In addition, we also determined the desaturation activity of S. constricta Δ6 Fad toward 24:5n-3 to give 24:6n-3, a key intermediate in docosahexaenoic acid (DHA) biosynthesis. Therefore, S. constricta is the first marine mollusc reported to possess all Fad and Elovl activities required for LC-PUFA biosynthesis via the 'Sprecher pathway'. This finding greatly increases our understanding of LC-PUFA biosynthesis in marine molluscs. Phylogenetic analysis by interrogating six marine molluscan genomes, and previously functionally characterized Elovl and Fad from marine molluscs, suggested that DHA biosynthetic ability was limited to a few species, due to the general lack of Δ4 or Δ6 Fad in most molluscs.

Keywords: Docosahexaenoic acid biosynthesis; Elongation of very long-chain fatty acids protein; Fatty acyl desaturases; Long-chain polyunsaturated fatty acids; Sinonovacula constricta.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bivalvia / enzymology
  • Bivalvia / metabolism*
  • Docosahexaenoic Acids / biosynthesis
  • Fatty Acid Desaturases / metabolism*
  • Fatty Acid Elongases / metabolism*
  • Fatty Acids, Unsaturated / biosynthesis*
  • Genome
  • Mollusca / genetics
  • Phylogeny

Substances

  • Fatty Acids, Unsaturated
  • Docosahexaenoic Acids
  • Fatty Acid Desaturases
  • Fatty Acid Elongases