WATER-SOLUBLE LIPOPROTEINS FROM YOLK GRANULES IN SEA-URCHIN EGGS .2. CHEMICAL COMPOSITION

The chemical composition of yolk lipoproteins (YLP-1, 2, and 3) was determined. YLP-1, 2, and 3 were quite similar as regards the chemical composition of lipids, proteins, and carbohydrate moieties. Each lipoprotein has an average dry weight composition of lipids (55-72%) and apo-lipoproteins (28-45%) containing protein, hexose, hexosamine, and sialic acid. In each lipoprotein, triacylglycerol is a major lipid component (70-83%), followed by phospholipid (8-16%), cholesterol (free and esterified, 8-10%), and free fatty acid (3-4%). Phosphatidylcholine and phosphatidylserine account for 68-74% and 16-24% of the phospholipids, respectively. The fatty acid compositions of total lipids from each lipoprotein are quite similar, with a high degree of unsaturation (63-65%). The carbohydrate content of apo-lipoproteins from each lipoprotein is remarkably high (27-31% of apo-lipoproteins) and their composition is very simple: mannose and glucosamine are major constituents in the polysaccharide moiety of each lipoprotein and sialic acid is all in the N-glycolyl form. The amino acid compositions of apo-lipoproteins are quite similar in YLP-1, 2, and 3, with high contents of aspartic acid, glutamic acid, threonine, serine, and leucine. Furthermore, a small amount of glycolipids is present in the yolk lipoproteins. They were separated into six components on TLC. All of them are resorcinol-positive, indicating the presence of sialoglycolipids. © 1979 By The Journal Of Biochemistry.