Polysaccharides enzymic solubilization

Other polysaccharides of primary cell walls.-A complex mixture of enzymes including endopolygalacturonase, pectin methylesterase, and/or pectin lyase solubilizes a mixture of polysaccharides from the primary cell walls of fruits [57-64]. Food scientists have referred for some 15 years to this mixture of polysaccharides as the hairy region to describe the highly branched character of the polysaccharides in the fraction and to emphasize the contrast to unbranched homogalacturonan. The recent discovery of rhamnogalacturonan hydrolase [65,66], which selectively cleaves the backbone of RG-I, led to the realization that the hairy... 

This paper begins with a brief description of pectin structure and an overview of the general mechanism of cell wall polysaccharide biosynthesis. This is followed by a summary of previous research on PGA-GalAT and a description of a facile method to synthesize UDP-[ Cj-galacturonic acid. Finally, the paper ends with a summary of our work on the identificadon, partial characterization, and initial solubilization of the homogalacturonan biosynthetic enzyme PGA-GalAT. 

Abiontic, involving free extracellular enzymes or solubilizing agents, enzymes bound to soil surfaces, enzymes within dead or non-proliferating cells, or enzymes associated with dead cell fragments. Extracellular enzymes are important in the initial stages of organic matter oxidation, in which polysaccharides and proteins are hydrolysed to soluble compounds that can be absorbed by microbial cells and further oxidized in biotic processes. 

Heller and Villemez299,300 solubilized, but did not separate, the D-mannosyltransferase and D-glucosyltransferase activities from this particulate-enzyme system, and found that, when only GDP-D-mannose is provided as the substrate, a/ -(1— 4)-linked D-mannan is synthesized and, when only GDP-D-glucose is present, ap-(l— 4)-linked D-glucan is produced. They further noted, with this transferase system, that incorporation of D-glucose from GDP-D-glucose into polysaccharide is a shortlived reaction that can be greatly extended if GDP-D-mannose is also included in the reaction mixture. 

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. 

Cellulose and complex pectic polysaccharides are the main matrix of the water-insoluble residue after centrifugation of fruit and vegetable homogenates. The use of pectinolytic enzymes is therefore necessary to solubilize the solid sample. Pectinolysis is known to degrade efficiently large pectic polysaccharides, but some of them, for example, rhamnogalacturonan-II, are considered to be resistant to pectinolytic enzymes [45]. A mixture of commercial products Rapi-dase LIQ and Pectinex Ultra-SPL , was reported for the release of metal-complexes from the solid parts of edible plants, fmits, and vegetables [45]. 

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