Abstracts now available online - Euro Fed Lipid

Very Long Chain Fatty Acids in sunflower oil: Occurrence and
Biosynthesis.
Joaquín J. Salas, Enrique Martínez-Force, Rafael Garcés, Instituto de la Grasa
Sevilla, Spain
Very long chain fatty acids (VLCFAs, those with more than 18 carbon atoms) occur in
small amounts in most seed oils. The main VLCFAs present in sunflower seeds are
arachidic, behenic and lignoceric, accounting for 1 to 3 % of the total fatty acids in the
triacylglycerols from common lines. Although these percentages are minor, the low
melting points of these fatty acids affected the behavior at low temperature of the
resulting oils.
VLCFA species are synthesized in the endoplasmic reticulum of by the action of the
dissociated enzyme complex called fatty acid elongase (FAE) from cytoplasmic
malonyl-CoA and acyl-CoAs exported from plastids. This reaction implies the
condensation of these substrates by the action a ketoacyl-CoA synthase followed by the
reduction and dehydration of the ketoacyl-CoA to yield a 2-C elongated acyl-CoA that is
ready for further elongation or incorporation into glycerolipids. The FAE complex was
characterized in sunflower seed kernels, where it was demonstrated to be mainly
dependent on NADPH. In this regard, two condensing enzymes with different substrate
specificities were solubilized and partially purified. These isoforms displayed strong
substrate inhibition kinetics and different optimum pH values. The content of VLCFA of
the oils from different sunflower mutants and the perspectives of the production of
improved sunflower oils will be discussed in function of the properties of these enzymes.
P12