Does triacylglycerol biosynthesis require diacylglycerol acyltransferase (DAGAT)?

Microsomal membrane preparations from the developing seeds of sunflower (He lianthus annuus L.) catalyse the conversion of sn-glycerol-3-phosphate and acyl-CoA to triacylglycerol via phosphatidic acid and diacylglycerol. The f ormation of diacylglycerol from phosphatidic acid was Mg2+ dependent and in the presence of EDTA phosphatidic acid accumulated. This property was used to generate large quantities of endogenous radioactive phosphatidic acid i n the membranes. On addition of Mg2+ the phosphatidic acid was used in tria cylglycerol formation. Acyl-CoA had little effect on the label which accumu lated in triacylglycerol from phosphatidic acid. Diacylglycerol acyltransfe rase, therefore, may not play a major role in oil formation as originally e nvisaged and other enzymes, including diacylglycerol: diacylglycerol transa cylase [Stobart, Mancha, Lenman, Dahlqvist and Stymne (1997) Planta 203, 58 -66] may have important biosynthetic functions.