Review_glycoprotein_production

Review_glycoprotein_production - N-glycosylation...

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1 N-glycosylation Engineering of Biopharmaceutical Expression Systems P.P. Jacobs 1,2 and *N. Callewaert 1,3 1 Department for Molecular Biomedical Research, VIB, Ghent, Belgium 2 Department of Molecular Biology, Ghent University, Ghent, Belgium 3 Department of Biochemistry, Physiology and Microbiology, Ghent University, Ghent, Belgium Keywords : N-glycosylation engineering, bacteria, mammalian cell culture, insect cells, yeast, plants, biopharmaceuticals ABSTRACT: N-glycosylation, the enzymatic coupling of oligosaccharides to specific asparagine residues of nascent polypeptide chains, is one of the most widespread post- translational modifications. Following transfer of an N-glycan precursor in the ER, this structure is further modified by a number of glycosidases and glycosyltransferases in the ER and the Golgi complex. The processing reactions occurring in the ER are highly conserved between lower and higher eukaryotes. In contrast, the reactions that take place in the Golgi complex are species- and cell type-specific. Due to its non-template driven nature, glycoproteins typically occur as a mixture of glycoforms (identical amino acid sequence, different glycan). Since N- glycans influence circulation half-life, tissue distribution, and biological activity each glycoform has its own pharmacokinetic, pharmacodynamic and efficacy profile. Moreover, modification of glycoproteins with non-human oligosaccharides can result in undesired immunogenicity. Therefore, engineering of the N-glycosylation pathway of most currently used heterologous protein expression systems (bacteria, mammalian cells, insect cells, yeasts and plants) is actively pursued by several academic and industrial laboratories. These research efforts are in the first place directed at humanizing the N-glycosylation pathway and eliminating immunogenic glycotopes. Moreover, one wants to establish new structure-function relationships of different glycoforms, which helps to decreasing the complexity of the N-glycan repertoire towards one defined N-glycan structure. In this review, we discuss the most important recent milestones in the glycoengineering field.
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2 INTRODUCTION Since the sequencing of the human genome revealed a surprisingly low number of 20,000- 25,000 genes [1], more attention is being paid to post-transcriptional and post-translational events. Glycosylation – the enzymatic coupling of glycans to proteins and lipids – is the most widespread post-translational modification (PTM). The importance of glycosylation in generating proteome diversity is illustrated by several observations. First, the glycosylation machinery is encoded for by 1-2% of the human genome [2]. This includes all proteins that are in some way involved in the synthesis, modification, localization or binding of glycans [3]. Second, about 50% of all human proteins are glycosylated [4]. However, since glycosylation is not template driven and combinatorial modification with different types and numbers of glycans is possible, each single glycoprotein is invariably present as a
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This note was uploaded on 05/28/2010 for the course WE BIBI000000 taught by Professor Johangrooten during the Spring '10 term at Ghent University.

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Review_glycoprotein_production - N-glycosylation...

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