Polysaccharides enzymic hydrolysis

In examining the structure of a polysaccharide, it is convenient to consider the methods involved under the three main headings (a) quantitative analysis, (b) methylation, and (c) periodate oxidation. These techniques may be supplemented by partial or enzymic hydrolysis as the circumstances indicate. Each of these aspects of polysaccharide chemistry may be aided by the application of gas-liquid chromatography, either qualitative or quantitative, or both. Thus, separations impossible by other techniques may often be achieved, and analytical data obtained in a fraction of the time demanded by other methods. 

However, in the polysaccharides obtained from some mutant strains, there are deviations from this idealized structure.44 Xanthan is relatively resistant to enzymic hydrolysis, but it has been cleaved by an enzyme preparation from a Bacillus sp. at moderate temperatures and in the presence of buffer salts, yielding mono- and oligo-saccharides 45 A partially purified, enzyme preparation46 hydrolyzed deacetylated or depyruvated xanthan, and also xanthan from several wild-type and mutant strains of Xanthomonas. The release of reducing material varied little with xanthan preparations having differences in O-acetyl and pyruvic acetal contents. Under similar conditions of incubation, cellulase acted only on xanthan from mutant strains that had defective side-chain formation. 

Finally, this section would remain incomplete without a few comments on the applications of HPLC to a particular group of carbohydrates—polysaccharides—whose determination, both qualitatively and quantitatively, has received much less attention than the rest (56). This may be surprising when the importance of these compounds, in terms of both functional properties and nutrition, is considered, but it is not so surprising when the difficulty of the analyses required is studied. High-performance LC can be used in this field, either to characterize the polysaccharides per se or to study their carbohydrate composition and the nature of bonding after acid or enzymic hydrolysis. 

Water-soluble polysaccharide species with higher molecular weights can be readily degraded by enzymic hydrolysis with a mixture of pectinase and hemi-cellulase to release the dRG-II complex [45]. The same mixture was found to be efFcient to extract the dRG-II D metal complexes from water-insoluble residues of vegetables, owing to the destruction of the pectic structure [45]. 

A. I. Usov and E. G. Ivanova, Polysaccharides of algae. 31. Enzymic hydrolysis of agar-like polysaccharide from the red seaweed Rhodomela larix (Turn.) C. Ag, Sow J. Bioorg. Chem., 1 (1981) 572—579 (English translation from Bioorg. Khim., 7 (1981) 1060-1068). 

Fig. 40.—Agar-diffusion pattern of the acid hydrolyzate of antigens and anti-group L Streptococci serum (S) acid hydrolyzate of group L polysaccharide (well A) native group L polysaccharide (well N), and enzyme hydrolyzate of group L polysaccharide (well E). Photograph of the paper chromatogram, showing release of carbohydrate from the polysaccharide by 1 h of acid hydrolysis, and of enzyme hydrolysis for 6-h periods.

Hemicellulose-B(Table V) from sapwood gave a blue color with iodine, which disappeared after treatment with Takadiastase under carefully controlled conditions. The solution was found to contain n-glucose, and its reducing value was equivalent to 24.6% of hexosan. On the basis of analytical data, heartwood hemicellulose-B appeared to be similar in constitution to the polysaccharide (6 anhydro-n-xylose units and 1 0-methyl-hexuronic acid per structural unit) isolated- after prolonged enzymic hydrolysis of heartwood hemicellulose-A. 

This enzyme hydrolyses cell wall polysaccharides containing alternating copolymers of A-acetylglucosamine and M-acetylmuramic acid (Imoto et al., 1972). Maximal rates of hydrolysis and the highest affinities are achieved when six saccharide units are bound to the enzyme. Hydrolysis takes place between sites D and E in a cleft lined by the two... 

Goldsehmid and Perlin have isolated, by enzymic hydrolysis of an arabinoxylan from wheat flour, a tetrasaccharide which was shown to be 0-a-L-arabinofuranosyl-(l—>3)-0-[i3-D-xylopyranosyl-(l— )]-0- 8-D-xylopy-ranosyl-(1 4)-D-xylose. The L-arabinofuranose side-chains in this polysaccharide are thus present in the a-L configuration, in agreement with the above evidence. 

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