Coenzyme A-Independent Transacylation in Amnion-Derived (WISH) Cells

Total membranes or microsomal fractions prepared from the amnion-derived WISH cell line posses a coenzyme A-independent transacylase activity. The transacylase utilizes 1-alkenyl- and 1-alkyl-2-lysoglycerophospholipids as preferred accepters. Marginal transacylation was observed with 1-acyl-2-lysoglycerophospholipids. The reaction occurred in the presence of ethylene glycol bis(β-aminoethyl ether)-N,N′-tetraacetic acid and was not affected by phospholipase A2 inhibitors. Both 1-acyl- or 1-alkyl-glycerophosphocholines containing an arachidonoyl residue in the sn-2 position were effective as donors, while 2-oleoyl- or 2-palmitoyl-glycerophosphocholines were ineffective. The presence of the transacylase, the specificity of the substrates, and the stability of the 1-alkenyl bond provide a biochemical model that may explain the increased proportion of a highly enriched arachidonate-containing phosphatidylethanolamine-plasmalogens fraction that is found in amnion at term.