Carbohydrate Activation/Glycosylation

A -glycosylation sites in human proteins and 0-P-GlcNAc/phosphorylation sites respectively. CAZY (http //afmb.cnr-mrs.lr/CAZY/) is a comprehensive database for carbohydrate active enzymes (CAZYmes). CAZYmes are classified into seqnence-derived fanulies (Davis and Henrissat, 2002). They are modular, consisting of one or more catalytic domains in harness with many noncatalytic modules, which often posses a carbohydrate binding functionality. Active-site residues, molecular mechanisms and 3D structures are all conserved within families. 

CAZy Carbohydrate-Active enZymes Protein sequence and structure links for glycoside hydrolases, glycosyl transferase, and other carbohydrate-active enzymes from all species www.cazy.org... 

The assembly of the complex Le carbohydrates has also been reported by Nicolaou, using a strategy based on glycosyl fluorides as donors (Scheme 6.19) [60]. The approach underscores the chemical stability of thioglycosides, which were also employed to protect the anomeric centers (e.g., 109 and 110). The thioglycosides are smoothly converted into the active glycosyl fluor-... 

Carbohydrates play a major role in protein bioactivity, bioavailability, and antigenicity therefore, the understanding of the glycosylation of protein molecules is very important in the development of effective glycoprotein therapeutics.172 In recent years, there has been considerable activity in the development of simple, rapid, and reliable separation methods for the analysis of... 

As detailed structural information is obtained from a greater diversity of parasitic nematodes it is expected that the occurrence of stage-specific carbohydrate antigens, and therefore stage-specific glycosyl transferase activities, will be identified as a common characteristic. 

Some reports even indicate that the conjugation of proteins or peptides with carbohydrates can increase dramatically their activity compared to that of the native state (Susaki et al., 1998). Carbohydrates also can provide a protective effect on modified peptides toward proteolytic digestion (Rudd et al., 1994) or mask recognition of a peptide by the immune system (Harding et al., 1993). The creation of neoglycoproteins thus can affect the activity of peptides and proteins, which are not normally glycosylated in vivo. 

Mammalian cell culture is more technically complex and more expensive than microbial cell fermentation. Therefore, it is usually only used in the manufacture of therapeutic proteins that show extensive and essential post-translational modifications. In practice, this usually refers to glycosylation, and the use of animal cell culture would be appropriate where the carbohydrate content and pattern are essential to the protein s biological activity, its stability or serum half-life. Therapeutic proteins falling into this category include EPO (Chapter 10), the gonadotrophins (Chapter 11), some cytokines (Chapters 8-10) and intact monoclonal antibodies (Chapter 13). 

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