Role of Cholinephosphotransferase and Diacylglycerol Acyltransferase in Channeling Unusual Fatty Acids into the Triacylglycerol Pool During Oilseed Development

Abstract

Cholinephosphotransferases (CPTs) from developing cotyledons of safflower, rapeseed, Cuphea and developing endosperm from castor bean were unable to discriminate between diacylglycerol (DAG) species contg. C18 and those contg. 10:0, 22:1, and/or 18:1-OH fatty acids. It is therefore unlikely that this enzyme plays a central role in excluding unusual fatty acids from the membrane pool of phosphatidylcholine. In contrast, DAG acyltransferase from castor bean endosperm showed a strong preference for DAG species contg. two ricinoleic acid residues. This indicates that this enzyme is involved in channeling ricinoleic acid, a membrane incompatible fatty acid, into the storage triacylglycerols (TAGs). The fact that CPT in the same plant tissue cannot exclude this DAG mol. species from the prodn. of phosphatidylcholine suggests that the biosynthesis of membrane glycerolipids is spatially sepd. from that of TAGs. [on SciFinder(R)]