Positional asymmetry of fatty acids on lecithin.

The possibility that naturally occurring lecithins may contain 1 molecule each of a saturated and an unsaturated fatty acid has never been shown. The data of Levene and Rolf (1) on the brominated lecithins from liver could be interpreted as indirect support for this theory. However, the evidence provided by Contardi and Latzer (2), Snider and Bloor (3), and Sinclair (4) on the fatty acid composition of various phospholipide fractions casts doubt on the validity of this proposition. On the other hand, it is well to point out that the latter investigators worked with phospholipides which were not well characterized, and the homogeneity of these components was not assured. A reinvestigation of the distribution of fatty acids in naturally occurring lecithins was prompted by the availability of a method for the preparation of highly purified lecithins (5) and the proof that lecithinase A releases fatty acid only from the a’-ester linkage of these compounds (6). Particular attention was directed towards the arrangement of the fatty acids of lecithins of beef, rabbit, rat, dog, and guinea pig liver.