ORGAN-SPECIFIC AND DEVELOPMENT-SPECIFIC ACYL COENZYME-A LYSOPHOSPHATIDATE ACYLTRANSFERASES IN PALM AND MEADOWFOAM

Of the three acyl coenzyme A acyltransferases (AT) directly involved in the assembly of fatty acids into triacylglycerols (TAG) in maturing seed, lysophosphatidate (LPA) AT has the highest substrate stringence and dictates which fatty acids can be used. We studied LPA-AT in the microsomes from various organs of palm (Syragrus cocoides) and found that only the microsomes from maturing seed could act on 1-lauroyl-LPA and lauroyl-coenzyme A to produce dilauroyl-phosphatidate. Similarly, of the microsomes from various organs of meadowfoam (Limnanthes alba), only those from maturing seed were active with 1-erucoyl-LPA and erucoylcoenzyme A to generate dierucoyl-phosphatidate. During maturation of the seeds of both species, the pattern of appearance of LPA-AT that produced dioleoyl phosphatidate was different from that of LPA-AT that generated dilauroyl or dierucoyl phosphatidate. The results show that in seeds, at least those that contain unusual fatty acids in the storage TAG, LPA-AT for the synthesis of TAG is different from the enzyme(s) for the synthesis of membrane lipids. They also suggest that there may be distinct pathways and/or compartments for the synthesis of TAG and membrane phospholipids.