Derivatives of Glycoproteins

Immobilized Derivatives of Glycoproteins. — The modification of glycoproteins to yield biologically active immobilized derivatives continues to attract much attention. These derivatives and their uses are summarized in Table 

Anti-[a-amylase inhibitor (Phaseolus vulgaris)] antibody AntHcarboxypeptidase N) antibody 

Reaction with agarose cyclic imido-carbonate 

Glutaraldehyde-mediated reaction with aminopropyl-silica gel Carbodi-imide mediated reaction with aminoethyl-agarose 

Affinity chromatography on immobilized concanavalin A in the presence of sodium dodecyl sulphate has been used in separations of glycoproteins.  

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Bemacki, R. J., and Bosmann, H. B., 1973, Rat-liver-sialidase activity utilizing a tritium-labeled sialic acid derivative of glycoprotein substrates, Eur. J. Biochem. 34 425-433. 

Puromycin. Puromycin (19), elaborated by S. alboniger (1—4), inhibits protein synthesis by replacing aminoacyl-tRNA at the A-site of peptidyltransferase (48,49). Photosensitive analogues of (19) have been used to label the A-site proteins of peptidyltransferase and tRNA (30). Compound (19), and its carbocycHc analogue have been used to study the accumulation of glycoprotein-derived free sialooligosaccharides, accumulation of mRNA, methylase activity, enzyme transport, rat embryo development, the acceptor site of human placental 80S ribosomes, and gene expression in mammalian cells (51—60). 

A biomolecular system of glycoproteins derived from bacterial cell envelopes that spontaneously aggregates to form crystalline arrays in the mesoscopic range is reviewed in Chapter 9. The structure and features of these S-layers that can be applied in biotechnology, membrane biomimetics, sensors, and vaccine development are discussed. 

Hydrazide groups can react with carbonyl groups to form stable hydrazone linkages. Derivatives of proteins formed from the reaction of their carboxylate side chains with adipic acid dihydrazide (Chapter 4, Section 8.1) and the water-soluble carbodiimide EDC (Chapter 3, Section 1.1) create activated proteins that can covalently bind to formyl residues. Hydrazide-modified enzymes prepared in this manner can bind specifically to aldehyde groups formed by mild periodate oxidation of carbohydrates (Chapter 1, Section 4.4). These reagents can be used in assay systems to detect or measure glycoproteins in cells, tissue sections, or blots (Gershoni et al., 1985). 

Multiple-ion monitoring is, however, of considerable value in structural studies, but only if model compounds of known structure are available for comparison. Such an approach has been used in the study of the carbohydrate structures of glycoproteins from different tissues.50 Separation of glycopeptides obtained from various tissues was performed on columns of concanavalin A-Sepharose. Structural analysis by multiple-ion monitoring of partially methylated, alditol acetates derived from the various fractions indicated that the glycopeptides were separated according to the linkage pattern of mannose (see Fig. 1). 

The second approach - animation glycosylisothiocyanates was suggested by E. Fisher [3,7], The method was widely used in the synthesis of analogs of glycoproteins and nucleosides of pirimidine and geterocyclic derivatives of the carbohydrates [7-8],... 

Kakehi, K., and Honda, S. (1996). Analysis of glycoproteins, glycopeptides and glycoprotein-derived oligosaccharides by high-performance capillary electrophoresis.. Chromatogr. A 720, 377-393. 

Enzymic hydrolysis is a useful tool for the identification of carbohydrate linkages, as well as for hydrolysis of the (labile) sialic acids. Neeser developed a method wherein the sialic acids are enzymically hydrolyzed and, simultaneously, enzymically converted into stable 2-amino-2-deoxymannose derivatives. This allows determination of carbohydrate constituents of glycoproteins in a single flask. 

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