Optimization of In Vitro N-Deglycosylation of Ovomucoid Protein

Glycoproteins have a wide distribution in nature and serve a vast number of functions. Of all the biologically occurring macromolecules, the glycoproteins, which consist of carbohydrate moieties covalently linked to a polypeptide backbone, represent the most diverse group, ranging from substances in which the carbohydrate component represents less than 1% of the total weight to those in which it represents over 80% of the total [1]. Glycosylation is a common posttranscriptional modification of proteins. Covalently bound sugar residues stabilize proteins, act as recognition sites, and provide loci for immuno response [2]. Carbohydrate modifications of proteins fall into three general categories: N-linked modification of asparagine (Asn), O-linked modification of serine or threonine and glycosylphosphatidyl inositol derivatization of the C-terminus carboxyl group [3]. Each of these transformations is catalyzed by one or more enzymes which demonstrate different peptide sequence requirements and reaction specificities. In particular, N-linked glycosylation is catalyzed by a single enzyme, oligosaccharyl transferase (OT), and involves the co-translational transfer of a lipid-linked tetradecasaccharide (GIcNAca-Mang-Glc3) to an Asn side chain within a nascent polypeptide [4,5].