Isolation and characterization of high molecular weight glycoproteins from embryonated eggs of Emerita asiatica

Abstract

The main yolk protein of Emerita asiatica is comprised of glycolipoprotein conjugated to carotenoid pigment. In the present study the embroynated eggs of the mole crab, Emerita asiatica, were tested for the presence of O-linked glycoproteins. The high molecular weight glycoprotein was extracted in 0.2 M phosphate buffer, pH 6.0 with 8 M urea and fractionated by size exclusion chromatography on Sephorase CL 4B column using the same buffer system. The high molecular weight glycoprotein was excluded and the included peak contained low molecular weight glycoproteins. The rechromatographed void fraction from the delipidated egg homogenate was free of low molecular weight components as confirmed by SDS-PAGE. 125I wheat germ agglutinin and peanut agglutinin overlay and the recently developed modified Morgan-Elson assay confirm that the egg contains mucin-type glycoproteins. Monosaccharide analysis of the void fraction was performed. High performance anionic exchange chromatography (HPAEC) shows the presence of GaINAc, GIcNAc, galactose, fucose, mannose and glucose. The identified and characterized high molecular weight glycoprotein is a new class which may play a role in the receptor mediated uptake of vitellogenin, a yolk precursor protein synthesized elsewhere.