Tagged sialyltransferase proteins

1. A tagged sialyltransferase protein comprising a sialyltransferase polypeptide, wherein the sialyltransferase polypeptide comprises an amino acid sequence with at least 95% amino acid sequence identity to SEQ ID NO: 4, wherein the sialyltransferase polypeptide has a methionine-glycine-serine (MGS) tag at the amino terminus, and wherein the tagged sialyltransferase protein has sialyltransferase activity.

2. The tagged sialyltransferase protein of claim 1 , wherein the sialyltransferase polypeptide is truncated.

3. The tagged sialyltransferase of claim 1 , wherein the sialyltransferase polypeptide is SEQ ID NO: 4.

4. The tagged sialyltransferase protein of claim 1 , wherein the protein begins with a mixture of methionine, glycine or serine.

5. A tagged sialyltransferase protein comprising a sialyltransferase polypeptide, wherein the sialyltransferase polypeptide comprises an amino acid sequence with at least 95% amino acid sequence identity to SEQ ID NO:4, wherein the sialyltransferase polypeptide has a methionine-glycine-serine (MGS) tag at the amino terminus, wherein the sialyltransferase polypeptide comprises sialyltransferase motif A (SEQ ID NO: 11) and sialyltransferase motif B (SEQ ID NO: 12), and wherein the tagged sialyltransferase protein has sialyltransferase activity.

6. A method of producing a sialylated oligosaccharide product comprising:

a) contacting an acceptor substrate comprising an oligosaccharide with the tagged sialyltransferase of claim 1 , and with a donor substrate comprising a sialic acid moiety; and

b) allowing transfer of the sialic acid moiety from the donor substrate to the acceptor substrate, thereby producing the sialylated oligosaccharide product.

7. The method of claim 6 , wherein the sialylated oligosaccharide product is produced in vitro.

8. The method of claim 6 , wherein the sialylated oligosaccharide product is produced in vivo.