Acyl-CoA: Lysophospholipid Acyltransferases

Cell membranes contain several classes of glycerophospholipids, which have numerous structural and functional roles in the cells. Polyunsaturated fatty acids, including arachidonic acid and eicosapentaenoic acid, are located at the sn-2 (but not sn-1)-position of glycerophospholipids in an asymmetrical manner. Using acyl-CoAs as donors, glycerophospholipids are formed by a de novo pathway (Kennedy pathway) and modified by a remodeling pathway (Lands' cycle) to generate membrane asymmetry and diversity. Both pathways were reported in the 1950s. Whereas enzymes involved in the Kennedy pathway have been well characterized, including enzymes in the 1-acylglycerol-3-phosphate O-acyltransferase family, little is known about enzymes involved in the Lands' cycle. Recently, several laboratories, including ours, isolated enzymes working in the remodeling pathway. These enzymes were discovered not only in the 1-acylglycerol-3-phosphate O-acyltransferase family but also in the membrane-bound O-acyltransferase family. In this review, we summarize recent studies on cloning and characterization of lysophospholipid acyltransferases that contribute to membrane asymmetry and diversity.