Isolation and Properties of a New Type of Sialopolysaccharide-Protein Complex from the Jelly Coat of Sea Urchin Eggs

A heteropolysaccharide-protein complex containing 70% sialic acid was isolated from the jelly coat of the eggs of the sea urchin, Pseudocentrotus depressus. The yield of this sialopolysaccharide-protein complex was 0.32% of the whole jelly powder. Purified by centrifugation and chromatography on Bio-Gel, the complex was found to be homogeneous by the criteria of electrophoresis and ultracentrifugation. Its sedimentation coefficient, s020 ,w, was 5.1, and the material carried a strong negative charge. The carbohydrate composition of the complex, expressed in percentages of the dry weight, was sialic acid, 70.0; fucose, 9.2; hexose, 3.7; and hexosamine, 2.4. Analyses for glycolic acid strongly indicated that all of the sialic acid occurred in glycolyl form. The molar ratio of sulfate to fucose was 1.42:1. The combined weights of monosaccharide, sulfate, and amino acid residues accounted for 96.0% of the complex weight. Thin layer chromatography of the sialopolysaccharide-protein complex after hydrolysis in mild acid showed five spots stained by Ehrlich's reagent. The major spot migrated as N-glycolylneuraminic acid. No indication of N-acetylneuraminic acid appeared. It is proposed that there are several new, undescribed neuraminic acids in the jelly coat, since the sialic acid yielded only 45% of the color in the reaction with thiobarbituric acid as compared with the direct Ehrlich assay and, moreover, no release of sialic acid from the complex by neuraminidase treatment was obtained.