Pectins structure

Keywords Arabinogalactans Bioactivity Medicinal plants Rhamnogalacturonans Pectins Structure-activity relations... 

Complex Pectins Structure elucidation using enzymes... 

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. 

BeMiller, J.N. (1986) An Introduction to Pectins Structure and Properties. In Chemistry and Function of Pectins, edited by M.L. Fishman, et al, pp. 2-12. American Chemical Society, Washington, DC. 

McCann, M.C., Shi, J., Roberts, K., and Carpita, N.C. (1994) Changes in pectin structure and localization during the growth of unadapted and NaCl-adapted tobacco cells. Plants. 5 773-785. 

Spatial variation in pectin structure and cation binding... 

Milieu conditions in gastrointestinal tract can influence the pectin structure and properties. Under the acid conditions of the stomach (pH 2-4) extraction of pectin from plant cell walls and hydrolysis of side chains can occur. In small intestine (pH 5-6) -elimination of main chains or de-esterification seems to be possible. In caecum and colon (pH 6-8) a strong fermentation of pectin takes place causing depolymerization to oligomers and leading to formation of short chain fatty acids and gases. The presence of OligoGalA is not yet clarified. 

Figure 1. Schematic representation of pectin structure indicating stabilization of catenated polygalacturonic acid chains through Ca + (O) cross-bridging. Non-bridging sequences of a(l-4) linked /S-galacturonic acid methylester extend from L-rhamnose via (1-4) linkage to another rhamnose via a(l-2) linkages. Arabinogalactan side chains are linked to rhamnose residues and couple the RG structure to hemicellulose.

Goldstein, I. J. Pectin Structure-Activity The Story Is Never Over. J. Agric. Food Chem. 2002, 50, 6583-6585. 

An irradiation dose of 1.0 kGy treatment decreased mesophilic bacteria in Mexican salads (Erickson, 2008). However, irradiation can cause changes in pectin structure leading to texture loss and hence shelf life. Also, viruses seem to be relatively resistant to irradiation treatment and relative to vegetative cells, suggesting that doses delivered to inactive... 

Ridley, B. L., O Neill, M. A., Mohnen, D. (2001). Pectins structure, biosynthesis, and oligogalacturonide-related signaling. Phytochemistry, 57, 929-961. 

Contains a wealth of information on pectins and pectinases, including pectin structures, enzyme properties, and enzyme applications. 

Lopes da Silva, J. A. L. and Rao, M. A. 2006. Pectins Structure, functionality, and uses, in Food Polysaccharides and Their Applications Second Edition, Revised and Expanded,eds. A. M. Stephen, G. 0. Phillips, and P. A. Williams, pp. 353-411, CRC Press, Inc., Boca Raton, New York. 

After enzymatic destabilization of a pectin structure, the different components present in the primary wall layer can be removed easily in subsequent rinsing steps [Hardin and Kim, 2000 Vigneswaran et al., 2012b]. A proper interpretation of the enzymatic action on cotton fibers on a molecular basis was not possible because of the lack of structural knowledge of cotton fiber. 

Pectin is a linear macromolecule composed of D-galacturonic acid. This monomer unit could be partially replaced by L-rhamnose leading to a new structure named rhamnogalacturonan I. A third pectin structural type is rhamnogalacturonan II, which is a less frequent, but complex and highly branched polysaccharide (Thakur, 1997 Averous and Pollet, 2012]. 

The model of pectin structure described above fails to account for one feature of some pectinic acids, which is the presence of mannose in the molecule. In a few instances the disaccharide PDGIcApl,2DMan has been identified in hydrolysates. Presumably it arises from another short side chain, though it should be noted that the gum of Anogeissus leiocarpus is based on a core of the type (-4GlcpA l,2Manp l-) , which does not resemble any major group of polysaccharides. 

Further support for the transfer of neutral sugar from arabinogalactan to pectin has come from studies by Rubery and Northcote (1970), which also throw light upon some possible ways in which pectin structure is adapted to the state of cell growth. These are discussed in the following section. 

Brent L.R., Molcolm A.O., Debra M., Pectins Structure, biosynthesis and oUgosaccharide-related signahng. Phytochemistry, 57, 2001,929-967. 

Fig. 27. Schematic representation of the pectin structure. Reproduced from Ref. 157 with the permission from American Chemical Sodety. (Copyright 2003).

Dongowski G. Influence of pectin structure on the interaction with bile-acids under in-vitro conditions. Z Lebensm Unters Forsch. 1995 201 (4) 390-398. 

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