Carbohydrates in glycoproteins

The content by weight of carbohydrate in glycoproteins may vary from only a few percent to over 50 percent in some proteins in mucous secretions. Although the function of the polysaccharide in most glycoproteins is unknown, in some cases it may provide hydrophilicity, recognition, and points of noncovalent interaction with other proteins through lectin-like affinity binding. 

Chaplin used methanolysis for the analysis of carbohydrates in glycoproteins. His method was a variation of the foregoing procedures, with an improvement of using tert-hvAyX alcohol to remove hydrogen chloride by coevaporation, instead of prolonged trituration with silver carbonate. His method is useful for samples containing uronic acids and lipids. Mononen studied methanolysis, followed by deamination and reduction with borohydride, for determination of the monosaccharide constituents of glycoconjugates. This method was applied to a lipid-free, protein fraction of rat brain. 

Characterization of carbohydrates in glycoproteins has become an important task in the field of biotechnology, since a number of protein biopharmaceuticals are glycosylated. To gain detailed structural information, it would be advantageous to have a routine profiling method that can provide suitable samples for further analysis. 

Carr SA, Barr JR, Roberts GD, Anumula KR, Taylor PB. Identification of attachment sites and structural classes of asparagine-linked carbohydrates in glycoproteins. Methods Enzymol 1990 193 501-518. 

The hydroxyl at C-2 in D-ribose is absent in 2-deoxy-D-ribose. In Chapter 26 we shall see how derivatives of 2-deoxy-D-ribose, called deoxyribonucleotides, are the fundamental building blocks of deoxyribonucleic acid (DNA), the material responsible for storing genetic information. L-Fucose, the carbon chain of which terminates in a methyl rather than a CH2OH group, is often found as one of the carbohydrates in glycoproteins, such as those on the surface of red blood cells that determine blood type (Section 23.25). 

---