Transacylase formation of bis(monoacylglycerol)phosphate

Recent work within our laboratory has focused on the enzymes we hypothesize are involved in the biosynthesis of bis(monoacylglycerol)phosphate from ph osphatidylglycerol. Here we describe a transacylase, active at acidic pH va lues, isolated from a macrophage-like cell line, RAW 264.7. This enzyme acy lates the head group glycerol of sn-3:sn-1' lysophosphatidylglycerol to for m sn-3:sn-l' bis(monoacylglycerol)phosphate. Here we demonstrate that this enzyme uses two lysophosphatidylglycerol molecules, one as an acyl donor an d another as an acyl acceptor, and that the acyl contributions from all oth er lipids tested are comparatively minor. This enzyme prefers saturated acy l chains to monounsaturates, 16 and 18 carbon fatty acids over 14 carbon fa tty acids, and saturated acyl chains at the sn-l position to monounsaturate d acyl chains on the sn-2 carbon of lysophosphatidylglycerol. We present da ta which show the transacylase activity depends on the presence of a lipid- water interface and the lipid polymorphic state. (C) 1999 Elsevier Science B.V. All rights reserved.