Polysaccharides lyases

Oxidoreductases Transferases Hydrolases Lyases Isomerases Ligases Phenolic polymers, polyanilines, vinyl polymers Polysaccharides, cyclic oligosaccharides, polyesters Polysaccharides, polyesters, polycarbonates, poly(amino acid)s, polyphosphates... 

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... 

The hydroxyl groups at C-2 and C-3 are not essential for the catalytic reaction. McNicol and Baker233 showed that the endopectate lyases of Bacillus sphaericus and Bacillus polymyxa degrade the Vi antigen, the bacterial-surface polysaccharide containing a-D-(1 — 4)-linked residues of 2-acetamido-3-0-acetyl-2-deoxy-D-galac-topyranuronate, in the same way as its O-deacetylated derivative and D-galacturonan. 

These protruding structures may form catalytic sites or binding sites for small molecules. Remarkably, some polysaccharide modification enzymes of pathogenic bacteria are similar to enzymes of their host cells. For example, during cell development, pectin, a principal component in the primary cell wall of plants, is modified by its own pectin methylesterases that have /1-solenoid structures (Johansson et al, 2002) and in this respect, resemble pectin lyases secreted by bacteria to break down these structures (Lietzke et al., 1996). 

Akita, M., Suzuki, A., Kobayashi, T., Ito, S., and Yamane, T. (2001). The first structure of pectate lyase belonging to polysaccharide lyase family 3. Acta CrystaUogr. D Biol. Crystalhgr. 57, 1786-1792. 

Rye, C. S. Withers, S. G., The synthesis of a novel thio-linked disaccharide of chondroitin as a potential inhibitor of polysaccharide lyases. Carbohydr. Res. 2004, 339, 699-703. 

The fungus produces a (l-galactosidase, a rhamogalacturonan lyase, an acetylesterase, and perhaps two other proteins of unknown type that convert the polysaccharide into the toxic product. Lepidimoide has been reported to be phytotoxic to a variety of plants, but may also promote the growth of the plants in which it is produced. 

This enzyme [EC 4.2.2.3], also referred to as poly(j8-D-mannuronate) lyase and poly(mana) alginate lyase, catalyzes the eliminative cleavage of polysaccharides containing /3-D-mannuronate residues to give oligosaccharides with 4-deoxy-o -L-eryt/iro-hex-4-enopyranuro-nosyl groups at their ends. 

SCHEME 1. Action of a-(l 4)-glucan lyase on floridean starch (the monosaccharide derivatives, which are split from the nonreducing ends of the polysaccharide chains probably in the form of 2-hydroxyglucal, are tautomerized to the more stable 1,5-anhydro-D-fructose, 5). 

Thus, X may be a saccharide, a 1,2-glycal, a phosphate residue, a nucleoside diphosphate, or a polyprenol diphosphate and X the OH of water, an alcohol, and often a saccharide. It is convenient, however, to consider enzymes cleaving polysaccharide chains in one of four classes hydrolases, glycosyl transferases, lyases, and phosphorylases. These follow the general reactions discussed below. 

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