Synthesis of phosphatidylcholine in the chloroplast envelope after import of lysophosphatidylcholine from endoplasmic reticulum membranes.

Purified, intact chloroplasts from Allium porrum seedlings are able to synthesize phosphatidylcholine by acylating lysophosphatidylcholine (but not glycerophosphocholine) with acyl-CoAs. The acyltransferase activity is located in the envelope of chloroplasts. It is specific for lysophosphatidylcholine and the neosynthesized lipids have a C18 fatty acid esterified to the sn-2 position of the glycerol backbone ('eukaryotic lipids'). By preincubating endoplasmic reticulum membranes with labeled lysophosphatidylcholine, it was shown that this molecule could be transferred by a partition process from the endoplasmic reticulum to chloroplasts where they are acylated to yield phosphatidylcholine.