ISOLATION AND CHARACTERIZATION OF THE HIGH-DENSITY-LIPOPROTEINS FROM THE HEMOLYMPH AND OVARY OF THE PENAEID-SHRIMP PENAEUS-SEMISULCATUS (DEHAAN) - APOPROTEINS AND LIPIDS

The high-density lipoproteins (HDLs) found in the male and female hemo lymph of Penaeus semisulcatus de Haan were isolated by NaBr (1.22 g/ml ) followed by sucrose gradient (5-25%) ultracentrifugation. The male H DL contained one protein, lipoprotein 1 (LP1), composed of one 110-kDa peptide subunit. The female HDL contained two proteins: 1) the LP1 th at was immunoidentical to the male LP1 and was similarly composed of o ne 110-kDa peptide subunit and 2) vitellogenin (Vg), reacting positive ly with the rabbit antiserum generated against vitellin (Vt) that was isolated from vitellogenic ovaries. Both Vg and Vt consisted mainly of three polypeptide subunits (200, 120, and 80 kDa) as revealed by dena tured PAGE and Western blot. The LP1 from males or females did not rea ct with the Vt rabbit antiserum. Similarly, Vg and Vt did not react wi th the rabbit antiserum prepared against LPI. Phospholipids (PL) const ituted 71-76% of the total lipids in the hemolymph and HDLs of both ma le and female hemolymph. Cholesterol (Ch) amounted to 17-20%, and smal l amounts (5%) of diacylglycerols (DAG) were also carried by these HDL s. Both the PL and DAG contained highly unsaturated fatty acids (20:5 omega 3 and 22:6 omega 3) that are transported from the food or hepato pancreas to the tissues, including the vitellogenic ovaries in females . In the present study we show for the first time the separate lipid c omposition of female LP1 and Vg and compare them with the lipids attac hed to the Vt. Vg had a lower lipid content than LPI (540 and 1089 mg/ g protein, respectively). Differences were also found in the relative abundance of FL, Ch, and DAG classes in the LP1 in comparison with Vg. Furthermore, small amounts (similar to 3.8%) of triacylglycerols (TAG ) were found only in the hemolymph of vitellogenic females, and they w ere associated with the Vg. Although Vg and Vt were composed of simila r polypeptides, their lipid composition was different. Vt, in contrast to Vg, carried considerable amounts of TAG (similar to 22%) and only trace amounts of DAG. The significance of the TAG in the hemolymph of vitellogenic females is not known, and the functional relationship bet ween Vg and Vt requires future extensive studies. Lipids were not dete cted in hemocyanin that was purified from clotted hemolymph. (C) 1997 Wiley-Liss, Inc.