Protein Glycosylation

Protein glycosylation is a complex posttranslational modification that manipulates the biological activity and function of therapeutic glycoproteins. To date, a plethora of functions related to glycan composition have been described in the literature: from solubility, stability, cellular localization, molecular trafficking, self-recognition, clearance, transport, immunogenicity, and circulating half-life. Most recently, glycan composition has been the target of modification to enhance the safety and efficacy of glycoprotein therapeutics. These links between the complex nature of the glycans and their associated functions have raised serious concerns within the drug regulatory authorities across the world. Glycans are the most complex and heterogeneous class of molecules due to their non-template-driven biosynthetic process, consequently making glycan characterization difficult. There is no universal method available that can characterize the complete intact glycoprotein structure; it is essential to apply several orthogonal methods to measure individual parameters such as glycosylation site analysis, oligosaccharide sequence, and monosaccharide content of a therapeutic glycoprotein. In this article, we discuss various state-of-the-art glycoanalytical approaches and strategies for evaluating total glycoprotein structure and function.