Glucans enzymic analysis

In an earlier article1 on the application of enzymic techniques to the analysis of the structure of polysaccharides, the -d- and /3-D-glucans were discussed, as well as more-general aspects of the preparation and use of catabolic enzymes in such analyses. The present article describes enzymic contributions to knowledge of the structures of other polysaccharides, but an account of subsequent research on a- and jS-D-glucans is also included. 

The observation47 that the stability of the secondary-ordered structure of xanthan (and as a consequence, its susceptibility to hydrolysis by cellulase) is a function of temperature, pH, and ionic strength has allowed the application of enzymic techniques to structural analysis. Xanthan is hydrolyzed in salt-free, aqueous solutions at elevated temperatures that is, hydrolysis occurs if the chain is unordered. It was proposed that, at lower temperatures and in the presence of salt, the small side-chains organize around the (1 ->4)-/3-D-glucan backbone and protect it from hydrolysis. 

Several factors are critical for the accuracy and reproducibility of (3-glucan determination. As with any other analysis, some of these factors relate to the skills of the analyst. Parameters critical for (3-glucan analysis include the following discussed below sample homogeneity, particle size, enzyme purity, glucose standard, pipetting technique, and absorbance measurement. 

A pentasaccharide and a trisaccharide have been isolated from an enzymic hydrolyzate of hemicellulosic material from oat coleoptiles.224 Methylation analysis of their structures indicated that these compounds may derive from j8-D-(l — 4)-linked D-glucans having terminal D-xylopyranosyl groups on some 0-6 atoms. Xylo-glucans having these structural features are present in the primary cell-walls of dicotyledons.22411... 

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