One pot desialylation and glycopegylation of therapeutic peptides

A method of synthesizing a peptide conjugate comprising combining:

• (a) sialidase;
• (b) an enzyme capable of catalyzing the transfer of a glycosyl linking group;
• (c) a modified sugar;
• and
• (d) a peptide,
• wherein the method comprises
• (i) a desialylation step in which the sialidase removes a sialic acid residue from the peptide, thereby forming a desialyated peptide, and
• (ii) a conjugation step in which the enzyme capable of catalyzing the transfer of a glycosyl linking group transfers a modified sugar moiety from the modified sugar to an amino acid or glycosyl residue of the peptide,
• which desialylation and conjugation steps are performed in the same vessel, thereby synthesizing the peptide conjugate.