Enzymes of phospholipid metabolism: Localization in the cytoplasmic and outer membrane of the cell envelope of Escherichia coli and Salmonella typhimurium

Abstract The phospholipid biosynthetic enzymes of the cell envelope of Escherichia coli and Salmonella typhimurium had highest specific activities in the cytoplasmic membrane fraction and lowest specific activities in the outer membrane fraction obtained by isopycnic sucrose density gradient centrifugation of the total membrane fraction of lysozyme-EDTA spheroplasts. This finding suggests that the site of phospholipid synthesis is the cytoplasmic membrane. Several degradative enzymes of phospholipid metabolism had highest specific activities in the outer membrane fraction and lowest specific activities in the cytoplasmic membrane. These data suggest an intracellular separation of the degradative and biosynthetic enzymes of phospholipid metabolism.