Characterization of Phosvitin and Phosphopeptides of Rainbow Trout Eggs

Abstract

Rainbow trout egg phosvitin prepared by the method of WALLACE et al. had molecular weight of 20, 000 which was about half of 41, 000 of hen's egg yolk phosvitin. It contained 57 residues of serine per molecule, followed by 15 of arginine and 10 of aspartic acid, and also contained 7 residues of glucosamine, 5 of mannose, and 3 of galactose. The molar ratio of serine and phos-phate was 1:1, and all of the phosphate were released by β-elimination reaction. Other inorganic components such as iron and copper were not detected in the phosvitin.
The precipitates obtained from the trichloroacetic acid extracts of rainbow trout eggs by precipitating with ethanol were separated into glycoprotein, phosvitin, and phosphopeptides by gel filtration. The phosphopeptides were composed mainly of components having molecular weights of about 1, 300 and 5, 400. Serine content of phosphopeptides was similar to that of phosvitin, but the composition of several amino acids differed with each other. These results show that phosphopeptides are naturally occurring in the rainbow trout eggs. The amounts of phosvitin and phosphopeptides are 0.49g and 0.47g per 100g of the rainbow trout eggs, respectively, while hen's egg yolks were lacking in phosphopeptides.