Purification and characterization of vitellin from the mature ovaries of prawn, Penaeus chinensis

Purification and the characterization of ovarian vitellin of mature female prawn, Penaeus chinensis, were the objectives of this study. Mature ovaries were homogenized and purified with gel filtration, hydroxylapatite, polyacrylamide gel electrophoresis (PAGE) and electro-elution. Two forms of purified vitellin (Vn1,Vn2) were obtained with an apparent molecular weight of 380 kDa (Vn1) and 500 kDa (Vn2). These proteins reacted with antiserum raised against P. monodon vitellin, and they had a complete identity of an immunoprecipitation line when compared to the hemolymph vitellogenin of P. chinensis. Five subunits of Vn1 (105, 85, 78, 58 and 40 kDa) and three subunits of Vn2 (155, 85, 78 kDa) were detected with SDS-PAGE, Vn1 and Vn2 stained as a lipo-glyco-caroteno-phospho-protein and a glycophospho-protein, respectively. Vn1 was more abundant than Vn2. The amino acid composition of the purified Vn1 was determined. Difference in the number of polypeptide subunits - but a similarity in the amino acid composition - was observed between purified P. chinensis vitellogenin and vitellin. The biochemical characteristics might suggest that vitellogenin in hemolymph is incorporated into oocytes and then dissociated into two subunits (191 kDa and 85 kDa). One of the subunits (191 kDa) is partially digested and transformed into vitellin in combination with another subunit (85 kDa).