Starch, /3-amylase action enzymic degradation

The only example of this technique applied to the amylose component is that already described, of the action of Z-enzyme on the /3-limit dextrin. In the case of amylopectin, enzymic methods enable a distinction to be made between the proposed laminated and highly ramified structures (I and III, in Fig. 1, page 352). The method used by Peat and coworkers101 involves the successive action of /3-amylase and R-enzyme on waxy maize starch. /3-Amylolysis will degrade A-chains down to two or three units from the 6 —> 1-a-D interchain linkages. These latter linkages will protect the... 

The enzymic degradation and sjmthesis of starch has formed the basis of very extensive investigations, and it might be expected that the action of such enzymes is well understood. However, recent studies of detailed action-patterns have shown that some previous, widely accepted concepts require to be modified. Furthermore, in the case of the oZphc-amylases, order in the overwhelming mass of accumulated data is now becoming apparent. 

It must be conceded that there is one case where the products of amylase action are probably not primary products formed in this way. This is the degradation of starch with the amylase from Bacillus macerans. The cycloamyloses formed by this enzyme are probably not preformed in the starch (see also Section II, 10). 

II. The Enzymic Degradation of Starch and Glycogen 1. Action of Amylase... 

PRODUCTS OF THE ENZYMIC DEGRADATION OF STARCH AND GLYCOGEN 295 4. Action of Taka-amylase ... 

D-Glucose and malto-oligosaccharides (DP 9) in starch hydrolysates have been separated by h.p.l.c. Oxidized (sodium hypochlorite) starch has been degraded by the joint actions of amyloglucosidase and a- and 3-amylases. An unidentified, modified trisaccharide, which resisted further enzymic degradation, was isolated. 

FIGURE 6.3 Action of a-amylase family enzymes involved in degradation of starch. Arrows indicate points in the starch molecule where the enzyme attacks (Takata et al., 1992). 

Figure 4-19 Schematic Representation of the Action of Starch-Degrading Enzymes. (A) Amylose and amylopectin, (B) action of a-amylase on amylose and amylopectin, (C) action of a debranching enzyme on amylose and amylopectin, (D) action of amyloglucosidase and debranching enzyme on amylose and amylopectin. Source Reprinted from H.S. Olsen, Enzymic Production of Glucose Syrups, in Handbook of Starch Hydrolysis Products and Their Derivatives, M.W. Kearsley and S.Z. Dziedzic, eds., p. 36, 1995, Aspen Publishers, Inc.

With some natural starches or with glycogen it is possible that the action of the /5-amylase is stopped before all end chains are removed because the substrate molecule has so complicated a network of chains that the enzyme, which presumably has a large molecule, can not penetrate into the inner parts of the substrate molecule. This point has been stressed in the case of glycogen by Meyer and Jeanloz. These authors degraded the substrate by a short treatment with hydrochloric acid to the extent that all end chains were accessible for the enzyme and a true saccharification limit was reached. Experiments with different starches and... 

Attempts have been made to estimate the proportion of B-fraction by removal of the A-fraction through hydrolysis with various enzymes. Since it is now recognized that the B-fraction undergoes partial conversion, these estimates are of little value. Treatment of gelatinized cereal starches with certain amylases gives a flocculent precipitate, variously termed hemicellulose or amylocellulose. This appears to be a degraded A-fraction, rendered insoluble through adsorption of fatty acids present in the substratum and also by deterioration of the protective colloid action afforded by the B-fraction. 

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