O-Glycoproteinase is expressed in E. coli and is a highly specific glycoproteinase that can specifically recognize serine or threonine residues of mucin-type O-linked sugars (whether sialylated or not) and cleave them at their N-termini. It can produce O-glycopeptides suitable for mass spectrometry analysis. The enzyme contains a 6X His-Tag, which can be easily removed after the reaction.