The structure of rat liver triglycerides.

The fatty acid compositions at the 1-, 2-, and 3-positions(3) of rat liver triglycerides were determined by using pancreatic lipase and diglyceride kinase. The distribution of acids between the 1- and 3-positions is not random; rather each position has a characteristic composition. The relative abundance of species and positional isomers in the triglyceride mixture was predicted by using values from the stereospecific analysis and assuming that the composition of each position is independent of the other two. The total triglyceride was resolved into species by using TLC with silver nitrate and Silica Gel G, and the relative amounts corresponded closely with those predicted on the basis of this assumption.The major species were isolated, and the distribution of their fatty acids among the three glyceride positions was determined. From these data the relative amount of each positional isomer was calculated. The results indicate that the esterification of fatty acids at each position proceeds with a specificity that is not correlated with the composition of the other positions with the molecule.The relative abundance of the different liver triglyceride species is also found to be related in part to the composition of the 1,2-diglyceride units found in the lecithins of this tissue.