Enzymatic Degradation of Polysaccharides

Enzymes that cleave polysaccharides are of interest for plant foods. Examples are processes that occur in the ripening of fruit (cf. 18.1.3.3.2), in the processing of flour to cakes and pastries (cf 15.2.2.1), and in the degradation of cereals in preparation for alcoholic fermentation (cf 20.1.4). In addition, enzymes of this t) e are used in food technology (cf 2.7.2.2) and in carbohydrate analysis (cf Table 2.16 and 4.4.6). The following hydrolases are of special importance. 

This enzyme catalyzes the hydrolysis of 1,4-a-D-glucosidic bonds in polysaccharides (mechanism, 2.4.2.5), effecting successive removals of maltose units from the nonreducing end. Hydrolysis is linked to a Walden inversion at C-1, giving rise to 3-maltose. This inversion, which can be detected polarimetrically, represents a definite characteristic of an exoglycanase. 

In contrast to amylose, amylopectin is not completely hydrolyzed. All reaction stops even before branch points are reached. 

This glucoamylase starts at the nonreducing end of 1,4-a-D-glucans and successively liberates (3-D-glucose units. In amylopectin, a-1,6-branches are cleaved ca. 30 times slower than a-1,4-bonds. 

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The interest in enzymatic degradation of polysaccharides is strongly associated with their biomedical applications. The process is dependent on the polysaccharide structures and conformation. Enzymatic degradation of these biopolymers has received attention for many years and is becoming an attractive alternative to chemical and mechanical processes. 

ENZYMATIC DEGRADATION OF A SOLUBLE HAIRY PECTIC POLYSACCHARIDE FROM SOY... 

YangXB, Gao XD, Han F, Xu BS, SongYC, Tan RX, Purification, characterization and enzymatic degradation of YCP, a polysaccharide from marine filamentous fungus Phoma herbarum YS4108, Biochimie 87 747-754, 2005. 

Atkinson, R.G., Schroder, R., Hallett, I.C., Cohen, D., and MacRae, E.A. 2002. Overexpression of polygalacturonase in transgenic apple trees leads to a range of novel phenotypes involving changes in cell adhesion. Plant Physiol. 129 122-133. Bach, E. and Schollmeyer, E. 1992. An ultraviolet-spectrophotometric method with 2-cyano-acetamide for the determination of the enzymatic degradation of reducing polysaccharides. Anal. Biochem. 203 335-339. 

Huisman, M.M.H. H.A. Schols A.G.J. Voragen. Enzymatic degradation of cell wall polysaccharides from soybean meal. Carbohydr. Poly. 1999, 38, 299-307. 

Nakamura, A. H. Euruta H. Maeda T. Takao Y. Nagamatsu. Structural studies by stepwise enzymatic degradation of the main backbone of soybean soluble polysaccharides consisting of galactur-onan and rhamnogalacturonan. Biosci. Biotechnol. Biochem. 2002, 66, 1301-1313. 

Horn, S.J., Sikorski, P., Cederkvist, J.B. et al. 2006b. Costs and benefits of processivity in enzymatic degradation of recalcitrant polysaccharides. Proc. Natl. Acad. Sci. U. S. A. 103 18089-18094. 

Isomaltose a reducing disaccharide, composed of two molecules of n-glucopyranose linked 1,6-glycosi-dically. I. is formed by the enzymatic degradation of branched polysaccharides, e.g. amylopectin. I. is a stereoisomer of gentiobiose. 

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