MICROSOMAL LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE FROM A BRASSICA-OLERACEA CULTIVAR INCORPORATES ERUCIC-ACID INTO THE SN-2 POSITION OF SEED TRIACYLGLYCEROLS

Developing seeds from Brassica oleracea (L.) var botrytis cv Sesam wer e examined for the ability to biosynthesize and incorporate erucic aci d into triacylglycerols (TAGs). Seed embryos at mid-development contai ned a high concentration of erucic acid in diacylglycerols and TAGs, a nd substantial levels were also detected in free fatty acids, acyl-coe nzyme A (CoA), phosphatidic acid, and phosphatidylcholine. Homogenates and microsomal fractions from seeds at mid-development produced [C-14 ]eicosenoyl- and [C-14]erucoyl-CoAs from [C-14]oleoyl-CoA in the prese nce of malonyl-CoA and reducing equivalents in vitro. These fatty acid s were incorporated into TAGs via the Kennedy pathway. However, unlike most Brassicaceae, the B. oleracea was able to insert significant eru cic acid into the sn-2 position of TAGs. It was shown that the lysopho sphatidic acid acyltransferase (LPAT) incorporated erucic acid into th e sn-2 position of lyso-phosphatidic acid. The erucoyl-CoA: LPAT activ ity during seed development and the sn-2 erucic acid content of the TA G fraction in mature seed were compared to those in B. napus, Tropaeol um majus, and Limnanthes douglasii. There was a correlation between th e in vitro erucoyl-CoA:LPAT activity and the sn-2 erucic acid content in seed TAGs. To our knowledge, this is the first member of the Brassi caceae reported to have an LPAT able to use erucoyl-CoA. This observat ion has important implications for efforts being made to increase the erucic acid content in B. napus, to supply strategic industrial feedst ocks.