BIOCHEMICAL AND CALCIUM-BINDING PROPERTIES OF WATER-SOLUBLE PROTEINS ISOLATED FROM OTOLITHS OF THE TILAPIA, ORECHROMIS-NILOTICUS

1. Tilapia otoliths contained 2.3% proteins in weight. Water (EDTA)-soluble proteins accounted for 47.1% of the total proteins. 2. Water-soluble proteins were characterized by a high abundance of acidic amino acids and separated into five fractions (I-V) by ion-exchange chromatography. 3. Fraction V had the highest capacity of calcium binding. This fraction contained a high abundance of glutamic and aspartic acids. Threonine and methionine also occurred in relatively high abundance. 4. Each fraction except fraction II was subdivided into multiple bands by PAGE. SDS PAGE showed that most bands were comprised of subunit structures. 5. Most of the PAGE-banded proteins occurred in protein-polysaccharide complexes.