CMP-NEUAC-GAL-BETA-1-]4GLCNAC ALPHA-2-]6SIALYLTRANSFERASE CATALYZES NEUAC TRANSFER TO GLYCOLIPIDS

Using mammalian gene-overexpression system, in vitro catalytic activit ies of CMP-NeuAc:Gal beta 1-->4GlcNAc alpha 2-->6sialyltransferase on glycosphingolipid accepters were analyzed. We transfected the mammalia n expression vector containing the cDNA that was cloned from Daudi cel ls into COS-I cells, and selected monoclonal transfectants in the pres ence of G418. Although the transfected alpha 2-->6sialyltransferase ca n catalyze NeuAc transfer onto glycoprotein accepters more than glycol ipids based on kinetic analyses, the substantial synthesis of IV(6)Neu Ac-nLcOse(4)Cer was observed and the activities were 7- to 9-times hig her in the transfected cells than in the mock transfectants. In additi on, the transfected COS-I cells with alpha 2-->6sialyltransferase cDNA were revealed to contain a higher amount of ganglioside that has the terminal NeuAc alpha 2-->6Gal sequence in the in situ situation than t he mock transfectants. These results using transfectants, together wit h those using the purified enzyme protein, suggest that the alpha 2--> 6sialyltransferase enzyme from Daudi cells can also catalyze NeuAc tra nsfer in alpha 2-->6 linkage onto glycosphingolipid acceptors.