A System for Sialic Acid Transfer by Colominic Acid and a Sialidase that Preferentially Hydrolyzes Sialyl α-2,8 Linkages

A partially purified sialidase that preferentially hydrolyzes colominic acid, which is a homopolymer of N-Acetylneuraminic acid linked by α-2,8 linkages, was prepared from Bacteroides fragilis SBT3182. This enzyme had a K m of 0.63 mM for α-2,3-sialyllactose, 0.97 mM for α-2,6-sialyllactose, and 0.01 mM for colominic acid. Colominic acid was a good substrate of this enzyme. By using this kinetic property of the enzyme, we transferred sialic acid from colominic acid to lactose by the transferase activity of the sialidase. Both α-2,3-sialyllactose and α-2,6-sialyllactose were synthesized with a total yield of 0.14%. We also observed that the ratio of synthesized sialyllactose isomers changed with the reaction time while the yield was constant.