Abstract
LDL isolated from eggs of the sand crayfish Ibacus ciliatus had proteins of 8 to 15 kDa with proteinase activity, which was detected by casein SDS-PAGE, and digested native vitellogenin of sand crayfish. Ca2+ was essential for the proteinase activity of LDL and its activity was inhibited by EDTA. Addition of the digested vigellogenin to the native vitellogenin stimulated the proteolysis of the vitellogenin. It was revealed by casein SDS-PAGE that the vitellogenin digested by LDL had a protein of 100 kDa with proteinase activity, but native vitellogenin itself had no proteinase activity. These results indicate that the native vitellogenin has proteinase activity as a latent form and the proteinase activity appears after digestion of the vitellogenin by LDL. The pattern of apoliporoteins of the proteolyzed vitellogenin on a gel after SDS-PAGE was very similar to that of lipovitellin of eggs of sand crayfish. These results suggest that the LDL and the proteolyzed vitellogenin take part in the proteolytic processing of the vitellogenin into yolk proteins.
