Membrane lipid modifications: biosynthesis and identification of phosphatidyl-N-methyl-N-isopropylethanolamine in rat liver microsomes.

In previous studies on the modification of polar head groups of membrane phospholipids with the unnatural base analog, N-isopropylethanolamine, we reported an unidentified phospholipid in addition to phosphatidyl-N-isopropylethanolamine in the various membrane fractions of rat liver. The structure of this phospholipid has now been identified as phosphatidyl-N-methyl-N-isopropylethanolamine by nuclear magnetic resonance spectroscopy, and by chromatographic and enzymic analysis. In addition, we found that when rats were injected intraperitoneally with the N-methyl-N-isopropylethanolamine, 19% of the liver microsomal phospholipid was phosphatidyl-N-methyl-N-isopropylethanolamine.