Study of Synthesis Pathways of the Essential Polyunsaturated Fatty Acid 20:5n-3 in the Diatom <i>Chaetoceros Muelleri</i> Using ¹³C-Isotope Labeling

• Main Authors: Marine Remize, Frédéric Planchon, Ai Ning Loh, Fabienne Le Grand, Antoine Bideau, Nelly Le Goic, Elodie Fleury, Philippe Miner, Rudolph Corvaisier, Aswani Volety, Philippe Soudant
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Biomolecules
• Subjects: synthesis pathway; diatom; 20:5n-3 (EPA), Chaetoceros muelleri; acyl-editing mechanism; compound-specific isotope analysis
• Online Access: https://www.mdpi.com/2218-273X/10/5/797
• ISSN: 2218-273X

<b>: </b>The present study sought to characterize the synthesis pathways producing the essential polyunsaturated fatty acid (PUFA) 20:5n-3 (EPA). For this, the incorporation of ¹³C was experimentally monitored into 10 fatty acids (FA) during the growth of the diatom <i>Chaetoceros muelleri</i> for 24 h<i>.</i> <i>Chaetoceros muelleri</i> preferentially and quickly incorporated ¹³C into C₁₈ PUFAs such as 18:2n-6 and 18:3n-6 as well as 16:0 and 16:1n-7, which were thus highly ¹³C-enriched. During the experiment, 20:5n-3 and 16:3n-4 were among the least-enriched fatty acids. The calculation of the enrichment percentage ratio of a fatty acid B over its suspected precursor A allowed us to suggest that the diatom produced 20:5n-3 (EPA) by a combination between the n-3 (via 18:4n-3) and n-6 (via 18:3n-6 and 20:4n-6) synthesis pathways as well as the alternative ω-3 desaturase pathway (via 20:4n-6). In addition, as FA from polar lipids were generally more enriched in ¹³C than FA from neutral lipids, particularly for 18:1n-9, 18:2n-6 and 18:3n-6, the existence of acyl-editing mechanisms and connectivity between polar and neutral lipid fatty acid pools were also hypothesized. Because 16:3n-4 and 20:5n-3 presented the same concentration and enrichment dynamics, a structural and metabolic link was proposed between these two PUFAs in <i>C. muelleri</i>.