Pectin polymerization

Tannins are polyhydroxyphenols. They are soluble in water, aleohols and aeetone and ean eoagulate proteins. They are yielded by extraetion from wood substanee, bark, leaves and fruits. Other components of the extraction solutions are sugars, pectins and other polymeric carbohydrates, amino acids and other substances. The content of non-tannins can reduce wood failure and water resistance of glued bonds. The polymeric carbohydrates especially increase the viscosity of the extracts. 

The stems of the tree were foimd to contain polysaccharides consisting of arabinose, galactose and galacturonic acid and only minor amoimts of rham-nose. Structural studies indicate that the polymeric material consists of 1,4-linked galacturonic acid residues, terminal, 1,4-, 1,6- and 1,3,6 galactose units and terminal and 1,5-linked arabinofuranose residues. Further studies must be performed on this in order to determine what type of pectin it can be classified as. The Hnkage data indicate that both AG-I and AG-II are present. This polymer was shown to activate polyclonal B-cells [78]. 

Pectins is a general term for a group of natural polymers based on polymerized galacturonic acid partly esterified with methanol. In addition these polymers must be considered as copolymers due to existence of neutral sugar branched zones. [1]. Some uronic acid units may also be esterified on 0-2 or 0-3 position with acetic acid. The pectins occur in the cell wall of higher plants and control at least partly the mechanical properties, the ion exchange properties and the swelling of the cell walls. 

Kauss, H. and Swanson, A.L. (1969) Cooperation of enzymes responsible for polymerization and methylation in pectin biosynthesis. ZJ aturforsch. 24 28-33. 

The binding of the antibody is size-dependent. Only the preincubation of the antibodies with oligopectates of degree of polymerization (DP) > 9 inhibits the binding to pectin immobilized in the wells of an ELISA test (Fig. 9.a, b). The difference between dimerized DPS and DP9 oligomers lies in the fact that dimerized DP9 could accommodate five calcium ions between their two chains whereas DPS could only four, which is apparently insufficient for the complexes to resist thermal agitation. 

Intrigued by the finding that Eca PLs exhibit notable differences in their kinetics, HPAEC analyses were carried out to examine the products from the depolymerization of PGA and 31% esterified pectin. After 18 h of incubation with PGA, PL1 and PL2 had produced mainly di- and trimers. Similariy, main products of PL3 action were trimers, followed by dimers. Moreover, it was the only enzyme found to produce monomers from unesterified substrates with a degree of polymerization >3. Using 31% esterified pectin as a substrate, similar end products were released by the PLs as from PGA. In addition to the products described, traces of tetra- up to octamers were detectable. While PL1 and PL2 released di- and trimers at almost... 

Action pattern analyses of pectin degradation. HPAEC data of oligomers released from 68% esterified pectin by combinations of Eca PLs are graphically represented. Arrows indicate addition of the third enzyme. Products with degrees of polymerization ranging from 2 to 9 were detected. The graphs illustrate the generation of dimers (A), trimers ( ) and pentamers ( ). 

Figure 1. Time-course measurement of polygalacturonase (PG) activity in the culture filtrate of Colletotrichum lindemuthianum grown on pectin and HPLC-Dionex analysis of mono-, di- and tri-galacturonic acid residues simultaneously released in the culture medium. The data are the mean of three independent experiments or represent one typical experiment in the case of galacturonic acid (GalA) residues. DP= Galacturonic acid degree of polymerization.

The plant cell wall is a polymeric mesh consisting of cellulose, hemicellulose, pectin and protein. Cellulose and hemicellulose are integral components of the cell wall, but pectic substances are located mainly in the outer wall regions within the middle lamella (McNeil et ai, 1984). Pectic substances are more susceptible to enzymatic degradation, because they are more exposed than other cell wall components. Therefore, pectin-degrading enzymes may play a central role in the penetration of plant tissue by bacteria. 

Extrusion-cooking of cell-wall rich products (e.g. wheat bran, apple pomace, citrus peels, sugar-beet pulp, pea hulls.) led to an important solubilisation of polysaccharides of various types without extensive degradation of the polymeric structure. The possibility of obtaining gelled systems directly with the extruded pectin-rich materials was demonstrated. 

We tested the effect of substrate polymerisation level on the PemB specific activity. A mixture of methylated oligogalacturonides was obtained by digestion of 93% methylated pectin by the Aspergillus niger pectin lyase A (20). PemB was more than 100-fold more active on methylat oligogalacturonides than on polymeric pectin. 

We described here the characterisation of the pemB gene and its product the second PME of E. chrysanthemi. The biochemical analysis of the purified protein indicated that PemB is actually an enzyme that demethylates pectin, leading to formation of methanol and PGA. However, PemB is more active on methylated oligogalacturonides than on polymeric pectin. The activating effect of non-ionic detergents on PemB was never pointed out for other pectinases and it is a characteristic of many membrane enzymes (21). 

Low level wastes (LLW), 23 592. See also Low-level radioactive waste (LLW) from reactors, 77 598 Low-melting lead alloys, 14 779 Low-melting-point indium alloys, 14 196 Low-melting thiodiols, DBTDL-catalyzed step-growth solution and melt polymerization reaction of, 23 744 Low-methoxyl pectins (LM pectins), 4 728 13 69... 

Because the galacturonic acid units of pectin spend a significant portion of the time in the polymerized form, there is less decomposition than that of galacturonic acid standards subjected to the same conditions of hydrolysis. For this reason, correction factors for hydrolysis losses, under any conditions, can never be completely accurate therefore, it is preferable to cleave glycosidic linkages with the minimum of decomposition. 

N-Linked oligosaccharides, Degree of polymerization of neutral oligosaccharides, Degree of methylation and acetylation of pectin, High mannose oligosaccharides ... 

The major polymers that make up the wall are polysaccharides and lignin. These occur together with more minor but very important constituents such as protein and lipid. Water constitutes a major and very important material of young, primary walls (2). The lignin is transported in the form of its building units (these may be present as glucosides) and is polymerized within the wall. Those polysaccharides which make up the matrix of the wall (hemicelluloses and pectin material) are polymerized in the endomembrane system and are secreted in a preformed condition to the outside of the cell. Further modifications of the polysaccharides (such as acetylation) may occur within the wall after deposition. Cellulose is polymerized at the cell surface by a complex enzyme system transported to the plasma membrane (3). 

The interaction of Ca2+ with pectins is discussed. The role of carboxylic acid salt formation and the degree of polymerization are first considered in terms of electrostatic and/or cooperative specific interactions. Then the effect of the degree of esterification and that of the pattern of carboxylic group distribution are discussed pectin esterase forms blocks which behave as fully hydrolyzed polymers and favor aggregation. Finally, the role of the calcium addition on the degree of aggregation was established. All the data show the important role of molecular structure of the pectins on calcium interactions. 

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