%0 Journal Article
%T Identification and Quantification of Protein Glycosylation
%A Ziv Roth
%A Galit Yehezkel
%A Isam Khalaila
%J International Journal of Carbohydrate Chemistry
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/640923
%X Glycosylation is one of the most abundant posttranslation modifications of proteins, and accumulating evidence indicate that the vast majority of proteins in eukaryotes are glycosylated. Glycosylation plays a role in protein folding, interaction, stability, and mobility, as well as in signal transduction. Thus, by regulating protein activity, glycosylation is involved in the normal functioning of the cell and in the development of diseases. Indeed, in the past few decades there has been a growing realization of the importance of protein glycosylation, as aberrant glycosylation has been implicated in metabolic, neurodegenerative, and neoplastic diseases. Thus, the identification and quantification of protein-borne oligosaccharides have become increasingly important both in the basic sciences of biochemistry and glycobiology and in the applicative sciences, particularly biomedicine and biotechnology. Here, we review the state-of-the-art methodologies for the identification and quantification of oligosaccharides, specifically N- and O-glycosylated proteins. 1. Protein Glycosylation Carbohydrates are essential for cell metabolism and energy production and are building blocks of the extracellular matrix. Carbohydrates also play a role in a variety of biological processes, such as intra- and intercellular signaling and mediation of cell-cell interactions. In plants and animals alike, they may be found in various forms and structures¡ªmonosaccharides, oligosaccharides, or long and complex polysaccharides. Saccharides may be present in their free forms or they may be linked to other molecules, such as proteins and lipids. In proteoglycans the saccharide is the dominant component, whereas in glycoproteins, the saccharide constitutes only a small portion of the entire molecule. Protein glycosylation, that is, the attachment of a saccharide moiety to a protein, is a modification that occurs either cotranslationally or posttranslationally. The two major types of glycosylation, N-linked and O-linked, are both involved in the maintenance of protein conformation and activity, in protein protection from proteolytic degradation, and in protein intracellular trafficking and secretion [1]. N-glycan moieties also play a key role in the folding, processing, and secretion of proteins from the endoplasmic reticulum (ER) and the Golgi apparatus [1]. In the past few decades, growing attention has been directed to protein glycosylation in the biomedical field, since aberrant glycosylations have been associated with various congenital [2], metabolic, neurodegenerative [3], and
%U http://www.hindawi.com/journals/ijcc/2012/640923/