Isolation, purification and characterization of the egg-yolk proteins from the oocytes of the Indian freshwater murrel, Channa punctatus (Bloch).

ABSTRACT

In oviparous organisms, yolk accumulation in the oocytes is critical and indispensable for the development of the newly hatched young ones. In fish and many other oviparous vertebrates, the major constituents of the egg-yolk are synthesized as a precursor in the liver. The precursor is transported to the oocyte for uptake and cleaved into major yolk proteins lipovitellin, phosvitin and β’-components. The eggs of Channa punctatus are pelagic, have large oil globule and exceptionally high lipid content. Lipovitellin was isolated by single step gel filtration chromatography on Sepharose 6B. Purified native lipovitellin showed immunological reactivity with vitellogenin antiserum. Phosvitin isolated by phenol extraction method could not be visualized with routine protein staining methods, whereas incorporation of trivalent ions in the coomassie brilliant blue stained phosvitin. It was characterized by in vivo labeling of egg-yolk proteins with 32P. The molecular mass of murrel phosvitin was less than 14,000 kDa.