The involvement of phospholipid:diacylglycerol acyltransferases in triacylglycerol production.

We have characterized three CoA-independent types of enzyme, phospholipases, phospholipid:diacylglycerol acyltransferases (PDATs) and cholinephosphotransferases, responsible for the removal of unusual fatty acids from phosphatidylcholine (PC) in microsomal preparations from developing oil seeds. The metabolism of sn-2-[(14)C]acyl-PC was monitored in microsomal preparations from various oilseeds having either medium-chain, acetylenic, epoxy or hydroxy fatty acids as their major fatty acids in the oil. The results indicate that PDAT plays a major role in removing ricinoleic acid and vernolic acid from phospholipids in Ricinus communis and Crepis palaestina seeds, respectively. However, vernolic, crepenynic and capric acids are primarily removed from phospholipids by phospholipases in Euphorbia lagascae, Crepis rubra and elm seeds, respectively. Further, we show that significant PDAT activity is also present in vegetative tissues of Arabidopsis thaliana.