Incorporation of fatty acids into phospholipids of erythrocyte membranes

Incorporation of C14-labeled fatty acids into phospholipids by washed ghosts, prepared from human erythrocytes, required the addition of ATP and was markedly stimulated by MgCl2 and coenzyme A. Labeled palmitic acid from l-C14-palmitoyl CoA was incorporated in the absence of added cofactors, The extent of incorporation of linoleic acid was greater than that of oleic, palmitic, or stearic acids. Of the radioactive fatty acid taken up into phospholipids 80–90% was found in the lecithin fraction. Degradation of the lecithin with Crotalus adamanteus venom established that the labeled fatty acid was located entirely in the Β-position. When whole blood was incubated with labeled fatty acid it was also found that most of the radioactivity incorporated into the ghost phospholipids was in the Β-position of lecithin.Rat erythrocyte ghosts incorporated C14-linoleic acid into phospholipids at about the same rate as did human erythrocyte ghosts. Sheep erythrocyte ghosts (which contain little lecithin) incorporated very little fatty acid into phospholipids, and none into lecithin.