The structure of egg yolk triglycerides

The triglycerides isolated from egg yolk lipids were subjected to stereospecific analysis. A very high degree of asymmetry between positions 1 and 3 was found. Palmitic acid constituted over 70% of the fatty acids in position 1. Position 2 was occupied largely by oleic and linoleic acids and position 3 by oleic acid and a comparatively small amount of saturated fatty acids. The triglycerides were also separated according to degree of unsaturation by argentation chromatography and each fraction subjected to the stereospecific analysis procedure. Good agreement was found between the proportions of the various molecular species obtained in this way and those predicted assuming a 1-random, 2-random, 3-random arrangement of fatty acids in the intact triglycerides. There was evidence for some selectivity in the utilisation of fatty acids of different chain lengths in certain of the species, however. No simple biosynthetic relationship was apparent between the structure of the egg yolk triglycerides and the structures of egg phosphatidyl choline and ethanolamine reported by others, although there are some similarities in the arrangement of fatty acids in the triglycerides and phosphatidyl choline.