Sialylated Glycoproteins

A method of producing a sialylated IgG antibody preparation wherein at least 60% of the branched glycans on the Fc domain of the IgG antibodies comprise a terminal sialic acid on both the alpha 1,3 arm and the alpha 1,6 arm, the method comprising:

• providing an IgG antibody preparation;
• combining the IgG antibody preparation with a beta 1,4 galactosyltransferase and uridine diphosphate galactose a galactose donor to provide a galactosylation reaction mixture;
• incubating the galactosylation reaction mixture to allow galactosylation of branched glycans;
• adding a ST6 beta-galactoside alpha-2,6-sialyltransferase 1 having at least 95% identity to amino acids 95-416 of SEQ ID NO:1 and cytidine-5′-monophospho-N-acetylneuraminic acid (CMP-NANA) an ST6-Gal1 sialyltransferase and a sialic acid donor to the galactosylation reaction mixture to provide a sialylation reaction mixture;
• and
• incubating the sialylation reaction mixture for a sufficient period of time to allow least 60% of the branched glycans on the Fc domain of the IgG antibodies in the preparation to be sialylated on both the alpha 1,3 arm and on the alpha 1,6 arm, wherein additional CMP-NANA sialic acid donor is added to the sialylation reaction mixture during the incubation of the sialylation reaction mixture.