We have previously demonstrated that 2H distribution in fatty acids is non-statistical and can be related to isotopic discrimination during chain extension and desaturation. Petroselinic acid (C18:1 Delta(6)), a fatty acid characteristic of the seeds of the Apiaceae, has been shown to be biosynthesised from palmitoyl-ACP (C16:0) by two steps, catalysed by a dedicated Delta(4)-desaturase and an elongase. We have now demonstrated that the isotopic profile resulting from this pathway is similar to that of the classical plant fatty acid pathway but that the isotopic fingerprint from both the desaturase and elongase steps show important differences relative to oleic and linoleic acid biosynthesis.
