Factors affecting the expression of recombinant glycoproteins

N-glycosylation is both species and tissue specific with a series of membrane bound glycosidases and glycosyltransferases modifying the oligosaccharide as it moves through the endoplasmic reticulum (ER) and Golgi. Each of these individual enzymatic reactions may not go to completion; therefore giving rise to glycoforms of the polypeptide. Glycosylation patterns of recombinant proteins are relevant for the immunogenicity, the pharmacological activity, pharmacokinetic profile, solubility and stability of the protein. This review describes the effect of primary and the 3-dimensional structure of the protein on sequon occupancy. Heterogeneity due to cell specific glycosylation and tissue culture conditions are discussed with main emphasis on N-glycosylation sequon occupancy. The review also discusses how fully glycosylated with total sequon occupancy glycoproteins which are of prime relevance in the expression of pharmaceutically relevant glycoproteins can be obtained.