The Reacylation of Deacylated Derivatives of Diphosphatidylglycerol by Microsomes and Mitochondria from Rat Liver

Rat liver microsomes contain an enzyme which catalyzes the acylation by acyl Coenzyme A thioesters of di(1(1'')acyl-sn-glycero-3-phosphoryl)1',3'-sn-glycerol(di(lysophosphatidyl)glycerol) to a compound identified as either 1'(1-acyl-sn-glycero-3-phosphoryl)-3'(1'',2 diacyl-sn-glycero-3-phosphoryl)-sn-glycerol or the corresponding 1'(1,2 diacyl isomer) (phosphatidyllysophosphatidylglycerol). A small amount of diphosphatidylglycerol is also formed. Evidence was obtained for the presence of radioactivity in both 1(1'') acyl and 2(2'') acyl positions of the reaction products. The enzyme has a pH optimum of pH 8.5 and displays considerable activity at an even more alkaline pH. In this regard, the acyltransferase resembles the enzyme which catalyzes the acylation of the 1-acyl isomer of lysophosphatidylglycerol, but differs from that which carries out the acylation of the 1-acyl isomer of lysophosphatidylcholine. Under the conditions used, linoleate was incorporated less readily than either oleate or stearate. Rat liver mitochondria displayed slight acyltransferase activity at pH 7.4 and virtually none at pH 9.0.