Photoaffinity Labeling of Lysophosphatidylcholine Acyltransferase from Developing Castor Bean Endosperm

Abstract

Acyltransferases play key roles in the biosynthesis of phospholipids and triacylglycerol. The membrane-bound acyltransferases have proven to be extremely recalcitrant to biochemical purification. We have used photoaffinity ligands bearing azido groups for site-directed covalent labeling of proteins [1]. The method described here opens up a new and potentially rewarding approach for the identification of lysophosphatidylcholine (LPC) acyltransferase (EC 2.3.1.23) from developing castor bean (Ricinus communis L.) endosperm using [(3-iodo-4-azidosalicyl)-12-amino]dodecanoyl-CoA (ASD-CoA) and [(3-iodo-4-azidosalicyl)-12-amino]dodecanoyl-sn-glycerol-3-phosphocholine (N3-LPC). This enzyme catalyzes the acylation of LPC to form phosphatidylcholine (PC). It has been suggested that the levels of polyunsaturated fatty acids in oilseeds may largely be controlled by the action of this acyltransferase [2].