Purification of an alpha-2,8-sialyltransferase, a potential initiating enzyme for the biosynthesis of polysialic acid in human neuroblastoma cells.

alpha-2,8-Sialyltransferase has been purified from human neuroblastoma CHP-134 cells greater than 2900-fold. The key step in the purification was a substrate affinity column utilizing immobilized colominic acid. Several kinetic parameters of the enzyme were defined. Fetuin but not asialofetuin served as substrate. The product of the enzyme reaction was characterized as containing sialyl residues in alpha-2,8-linkage with the use of recombinant sialidases. It is suggested that the purified enzyme is an initiating enzyme for the biosynthesis of polysialic acid since these cells also have the activity of poly alpha-2,8-sialyltransferase and contain polysialic acid. This alpha-2,8-sialyltransferase may be a new member of a family of alpha-2,8-sialyltransferases recently described, since it differs in substrate specificity reported for the cloned and expressed enzymes.