LIPOSOME-MEDIATED ENZYMATIC-SYNTHESIS OF PHOSPHATIDYLCHOLINE AS AN APPROACH TO SELF-REPLICATING LIPOSOMES

The four enzymes of the salvage pathway for phosphatidylcholine synthesis sn-glycerol-3-phosphate acyltransferase, 1-acyl-sn-glycerol-3-phosphate acyltransferase, phosphatidate phosphatase, and cytidinediphosphocholine phosphocholinetransferase were simulataneously bound to soybean phosphatidylcholine liposomes. Evidence is presented that the entire enzyme chain is reconstituted in the liposomes, and that synthesis is preferentially localized in the proteliposomal membrane where the enzymes are present in an active bound form. Various phosphatidylcholines, differing in the alkyl group of the fatty acid moieties, can be synthesized in this way and incorporated into the host liposomes, with a corresponding change of the equilibrium size of the liposomes. The present system can then also be seen as a self-reproducing liposome, and the implication of this for chemical autopoiesis is briefly discussed.