Calcium interaction with pectins

Effect of Chemical Structure of Pectins on Their Interactions with Calcium... 

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. 

From circular dichroism, it appears that for pectins with a degree of neutralization (a ) of over 0.4, a specific interaction with calcium occurs... 

The interactions of pectins with mono- or divalent counterions eire of a great importance in many fields. It is well-known that these polyelectrolytes play an important role as natural ion-exchangers in plant physiology, phytopathology, nutrition (1-2) and their ability to form gels with calcium ions is widely used by food technologists (3). 

Since we are interested in trying to better understand the interaction of metal ions with the cucumber cell wall, it was of interest to develop a technique to determine the extent and affinity of ion binding in cucumber tissue. Since it is generally thought that calcium is bound to plant tissues by interacting with the free carboxyl groups present in pectin, an effort has been made to relate calcium bound in cucumber mesocarp tissue to the concentration of the free carboxyl groups of pectin. 

Rinaudo M., Effect of chemical structure of pectins on their interactions with calcium, in Plant Cell Wall Polymers Biogenesis and Biodegradation, Eds. Lewis G. and Paice M.G., ACS Symposium Series, American Chemical Society, Washington D.C., 1989, Chapter 23, pp. 324—332. 

Decreux, A. and Messiaen, J. (2005). Wall-associated kinase WAKl interacts with cell wall pectins in a calcium-induced conformation. Plant Cell Physiol. 46, 268-278. 

Low methoxylated (esterified) pectins can form gels in the presence of divalent cations, usually calcium. The interaction with calcium ions of fragments of two D-galacturonic acid adjacent units... 

With different pectins, one found that the activity coefficient of calcium has a value half that of magnesium this is interpreted as the basis of a dimer formation in presence of calcium. The specific interaction of calcium was described as the egg-box model first proposed for polyguluronate in which oxygen atoms coordinated to calcium [46]. Recently, the comparative behaviour of Mg and Ca with homogalacturonan was reexamined [47]. 

The role of the structural properties of pectins was described recently (1) where it was shown that interactions of calcium with pectic substances were directly related to the existence of unbranched and non-esterified galacturonic blocks. Calcium was able to ionically bind two or more chains... 

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