Polysaccharides glycosyl sequencing

Various techniques have been utilized for sequencing the glycosyl residues of polysaccharides and oligosaccharides. These techniques are elaborations of the commonplace procedure of converting polysaccharides, by partial hydrolysis, into structurally analyzable oligosaccharides. This conversion is generally achieved by partial hydrolysis with acid, by acetolysis,131 or by formolysis.62 These reagents may differ in the... 

The aim of the present Section is to discuss existing information concerning sequences of glycosylation reactions during the assembly of polysaccharide chains. Data concerning identification of intermediates in the process, and on solubilization and purification of the enzymes involved, are also included. 

The term monomeric mechanism will be used for the mechanism depicted in the left-hand part of Scheme 2 (sequence a). In this case, the monosaccharide residues are transferred consecutively from the corresponding glycosyl donors (Z-A or Z -B) onto a membrane-bound glycosyl acceptor. The acceptor is generally a monosaccharide residue, which may be a fragment of an oligosaccharide chain linked to a hydrophobic molecule embedded in a cell membrane. In many instances, the acceptor that is used for assembly of the polymeric chain (Y) is not identical to the final acceptor (X) of the chain, and further transfer of the chain from Y to X, or liberation of the polysaccharide molecule in the case of exocellular polysaccharides, is a necessary step in the biosynthesis. 

In addition to determining the monosaccharide composition, linkage types, and sequence of residues in a cell wall polysaccharide, it is also essential to determine the anomeric configuration of the glycosyl residues. As with determining the sequence of glycosyl residues, the method of choice, be it chemical, enzymic, or physical, are dependent on the type of material under investigation and the amount available. 

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