The substrate specificities of sunflower and soybean phospholipases D using transphosphatidylation reaction

BACKGROUND: Phospholipase D (PLD) belongs to a lipolytic enzyme subclass which catalyzes the hydrolysis and transesterification of glycerophospholipids at the terminal phosphodiester bond. RESULTS: In this work, we have studied the substrate specificity of PLDs from germinating sunflower seeds and cultured-soybean cells, using their capacity of transphosphatidylation. In the presence of a nucleophilic acceptor, such as [¹⁴C]ethanol, PLD catalyzes the production of phosphatidyl-[¹⁴C]-ethanol. The resulting product is easily identified since it is well separated from the other lipids by thin-layer chromatography. The main advantage of this assay is that the phospholipid used as substrate does not need to be radiolabelled and thus allow us a large choice of polar heads and fatty acids. In vitro, we observed that sunflower and soybean cell PLD show the following decreasing order of specificity: phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol; while phosphatidylserine and phosphatidylinositol are utilized much less efficiently. CONCLUSIONS: The substrate specificity is modulated by the fatty acid composition of the phosphatidylcholine used as well as by the presence of other charged phospholipids.