Oligosaccharide chains glycosaminoglycans

Saitoh H, Takagaki K, Majima M, Nakamura T, Matsuki A, Kasai M, Narita H, Endo M. Enzymic reconstruction of glycosaminoglycan oligosaccharide chains using the transglycosyla-tion reaction of bovine testicular hyaluronidase. J. Biol. Chem. 1995 270 3741-3747. 

Differences in the structure of glycoproteins can manifest themselves in a number of ways. Perhaps the first point to be emphasized is that the nature of the polypeptide chain to which oligosaccharide moieties become attached is not always the same. This is a situation that we have already discussed in connection with certain of the glycosaminoglycans (see p. 440). 

N-Acetylneuraminic acid N-Acetylneuraminic acid (NANA) is a member of the family of sialic acids, each of which is acylated at a different site. These compounds are usually found as terminal carbohydrate residues of oligosaccharide side chains of glycoproteins, glycolipids, or, less frequently, of glycosaminoglycans. The]... 

As well as chondroitin sulfate, other glycosaminoglycans, such as keratan sulfate, with shorter chains (Mr = 2,500-5,000) are found in cartilage (Fig. 5-22). N-linked oligosaccharides similar to those found in glycoproteins are also present. Note that keratan sulfate in other tissues, e.g., intervertebral disk or cornea, has a longer chain (Mr= 10,000-25,000) and may have a different oligosaccharide link to the core protein. 

The ido configuration is present, isolated in the middle of other monosaccharide residues, in the polycondensed chains called glycosaminoglycans of natural polysaccharides dermatan sulfate, heparan sulfate, and heparin. The derivative in question belonging to the L-series is 2-0-sulfo-L-iduronic acid. It is represented (2.34, R = R = H) in a non-conformational manner with the a-L-idopyrano configuration present in these polysaccharides. The L-ido residue is isolated in the sequence, in the centre of the chains attached to 0-1 and 0-4, respectively (Section 17.3). It is found as a mixture of the l- C4 (2.35) and l- Sq (2.36) conformations. The proportion of the skew form varies from 40 to 60% according to the attached oligosaccharide sequences, R and R (Casu et al. 1986). 

The term proteoglycan was introduced to describe an entire molecule consisting of one or more glycosaminoglycan chains attached to a core protein by means of a linkage oligosaccharide. For example the general term for an undefined proteoglycan... 

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