Production of sialyloligosaccharides by trans-sialidase catalyzed reaction using fetuin as a sialic acid donor

Typically, α-2,3-sialyllactose is used as the sialic acid donor in trans-sialidase catalyzed reaction. However, due to limitations such as reversibility and cost, alternative sialic acid donors are needed. Here we show that fetuin, a glycoprotein containing abundant sialic acids at the ends of its oligosaccharides, can be used as a sialic acid donor in trans-sialidase catalyzed reaction. Among 166 nmol of total sialic acid in milligrams fetuin, 125 nmol of sialic acid was consumed for the trans-sialidase reaction. The trans-sialidase reaction using fetuin was reversible. The sialyl transfer rate of fetuin to Galβ(1,4)GlcNAc was similar to that of α-2,3-sialyllactose and approximately 30–40 times greater than that of 4-methylumbelliferryl-α-sialic acid. trans-Sialidase reaction was performed using 200 mg of fetuin and 34 mg of lactose as a donor and an acceptor, respectively, and 8 mg of product, i.e. α-2,3-sialyllactose, was purified by gel filtration column. To simplify the purification step, trans-sialidase reaction was carried out by submerging and stirring a dialysis bag containing fetuin and trans-sialidase into a lactose solution.