The yolk proteins obtained from various stages of embryogenesis of rainbow trout were analyzed in order to determine their chemical and physical properties.
1. The yolk protein gradually changed its physical and chemical properties with the progressing of the embryogenesis. The increase of molecular size of the lipoprotein was observed in the gel filtration. It was suggested that the lipoprotein molecule was rearranged in the yolk sac after a partial degradation by embryo.
2. The amino acid composition of the rainbow trout egg lipoprotein was somewhat similar to that of lipovitellin, although the high value of alanine and the low content of serine, cystine, and tryptophane were characteristic for the former.
3. A decrease in the ratio of several amino acids in the lipoprotein was found from the 42nd-day after fertilization.
4. The amino acid composition of glycoprotein in both the unfertilized egg and 42nd-day yolk were similar to each other. Therefore the glycoprotein catabolized without consumption of specific amino acid.