Composition of rat liver triacylglycerols and diacylglycerols.

Abstract

Different fractions of rat liver triacylglycerols and X‐1,2‐diacylglycerols were prepared by thin‐layer chromatography on silver nitrate‐containing silica gel. The positional distribution of fatty acids in these fractions and unfractionated triacylglycerols and diacylglycerols was analyzed by a scaled‐down version of Brockerhoff's method. Both in tri‐ and diacylglycerols position 1 contains mainly saturated fatty acids, while most fatty acids in position 2 are unsaturated. Position 3 in triacylglycerols contains mainly unsaturated fatty acids and has a large proportion of highly unsaturated fatty acids. The relative abundance of different 1,2‐diacyl‐sn‐glycerol units in diacylglycerols and triacylglycerols was similar except for highly unsaturated units. This suggests a random utilization of 1,2‐diacyl‐sn‐glycerols with 1–3 double bonds for triacylglycerol biosynthesis. The highly unsaturated diacylglycerols probably originate from phospholipids. From the positional distribution of fatty acids in total triacylglycerols the proportions of different triacylglycerol fractions were predicted from the assumption that each fatty acid in any position is combined with fatty acids in proportion to their relative amounts in the other positions. The observed distribution agreed well with the predicted one‐.