Synthesis of a unique polysialoganglioside by polysialyltransferase from embryos of sea urchin Lytechinus pictus: Size determination of polysialic acid chain synthesized onto GD3 in vitro

It has been reported that polysialyltransferase in sea urchin embryos polysialylates 38 kDa endogenous acceptor proteins and disialyllactose moieties of mammalian ganglioside GD3, and its maximum activity was observed at gastrula stage using an excess of GD3 as an exogenous acceptor. The objective of the present investigation is to determine how many sialic acid residues are transferred onto the disialyllactose moiety of GD3 by the polysialyltransferase when it is used as an exogenous acceptor. Ceramide glycanase which can cleave the linkage between ceramide and sugar moiety was treated to obtain hydrophilic polysialyllactose from polysialylated GD3. Surprisingly, size analysis of these chains using non-SDS polyacrylamide gel electrophoresis showed that up to 60 sialic acid residues were transferred to the disialyllactose moiety of GD3 by polysialyltransferase from the sea urchin embryos.