Water-soluble lipoproteins from yolk granules in sea urchin eggs. II. 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 apolipoprotiens 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.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D005227:Fatty Acids / Q000032:analysis; D005260:Female; D008074:Lipoproteins / Q000032:analysis*; D010063:Ovum / Q000032:analysis; D012617:Sea Urchins; D015017:Yolk Sac / Q000032:analysis*
D000596:Amino Acids; D002241:Carbohydrates; D005227:Fatty Acids; D008074:Lipoproteins