Isolated from the bacteria Escherichia coli and Salmonella typhimurium. The enzyme prefers phosphatidylcholine with a palmitoyl group at the sn-1 position and palmitoyl or stearoyl groups at the sn-2 position. There is some activity with corresponding phosphatidylserines but only weak activity with other diacylphosphatidyl compounds. The enzyme also acts on Kdo-(2¡ú4)-Kdo-(2¡ú6)-lipid IVA.