Positional distribution of saturated and unsaturated fatty acids on egg lecithin

A method is described to determine the position of fatty acids on lecithin. Purified egg lecithin is enzymatically hydrolyzed to the corresponding mixture of α,β-diglycerides with lecithinase D. Myristic acid is incorporated into the α' position of the diglycerides and the resulting triglycerides are hydrolyzed with pancreatic lipase, which specifically cleaves fatty acids from the α and α` positions. Palmitic, myristic, and stearic acids were freed by the pancreatic lipase, proving that the saturated acids are on the α' position, while the unsaturated fatty acids occupy the β position of egg lecithin. Since snake venom lecithinase A removes the unsaturated acids from lecithin, the site of hydrolysis must be at the β position of lecithin