Dermatan sulfate peptides

There has been some doubt as to whether the serine-xylose bond is the only type of carbohydrate-protein linkage present, since treatment of dermatan sulfate-peptides with alkali resulted in destmction of only about one-quarter of the serine (Meyer ei al., 1965). In this context, a few comments are in order concerning the differentiation of linkage types on the basis of their sensitivity to alkali (Anderson et at, 1965 see also Gottschalk, 1966). Provided that the amino and carboxyl groups of serine or threonine are bound in peptide linkage or blocked in other ways, the -elimination reaction, which characteristically occurs on alkali treatment of polysaccharides bound to these amino acids, proceeds at a relatively rapid rate, and complete cleav e of the bonds takes place within a matter... 

In dermatan sulfate from shark skin, there is about a 40% excess of sulfate groups over 2-acetamido-2-deoxy-D-galactose residues.300 The small proportions of D-glucu-ronic acid (d-GUA) present in dermatan sulfate occur in regions of the carbohydrate chains both near to, and far from, the carbohydrate-peptide linkage region. The isolation of the tetrasaccharide... 

Other molecules have been suggested as being useful lung-specific bioadhesive agents [137,138], for example, insulin, transferrin, prostaglandins, hirudin-inhibited thrombin (which binds thrombomodulin), anionic polysaccharides, oligosaccharides (such as dextran sulfate, dermatan sulfate, chondroitin sulfate, hyaluronic acid), peptides (such as benzoyl-phe-ala-pro [BPAPI] that... 

The use of trypsin rather than papain for the initial proteolytic digestion of the tissue yields dermatan sulfate with a larger peptide moiety, and alkali treatment of such preparations results in destruction of approximately 90% of the serine residues (Stem et al., 1970). The polysaccharide isolated after such treatment is virtually devoid of amino acids, and it may therefore be concluded that serine does indeed participate in the majority of the carbohydrate-protein bonds. The lower degree of serine destruction observed with preparations obtained after more extensive proteolysis is presumably due to the factors indicated above, i.e., that a considerable proportion of the serine residues have free amino or carboxyl groups. 

The proof of this sequence, and of the nature of the carbohydrate-peptide bond, was based on enzymic erosion to a glycopeptide fragment that was then studied by adaptations of classical methods. A similar linkage-region probably occurs in heparin,86 heparitin sulfate,87 dermatan sulfate88 and chondroitin 6-sulfate.88a It is possible that the polypeptide core itself is branched.89... 

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