Poly-D-galacturonic acid

Fig. 1. — Effect47 of Tomato Pectinesterase on the Activity of Pectate Lyase Acting on Highly Esterified Pectin. [Reaction mixtures contained 0.5% of D-galacturonan (broken line) or poly(D-galacturonic acid methyl ester) methyl glycoside (solid lines), 5 mM CaCl2, 33 mM phosphate buflFer (pH 7.0), and 0.25 unit of lyase in a final volume of 3.0 ml. In addition, the reaction mixture represented by the middle curve contained 0.031 unit of tomato pectinesterase in a final volume of 3.3 ml.] Reprinted, with permission, from M. Lee and J. D. Macmillan, Biochemistry, 9, 1930-1934 (1970). Copyright by the American Chemical Society.

The infrared spectra of a large number of carbohydrates have been published aU of these will be useful for future comparative work. The work of Kuhn and of Stevenson and Levine has already been mentioned. In addition, Solms, Denzler and Deuel have recently pubUshed the spectra of several derivatives of poly-D-galacturonic acid. The collection of infrared spectra of the sugar acetates and related compounds also forms a valuable source of data for comparative work. ... 

A poly-D-galacturonate lyase released from Erwinia rubrifaciens cells by osmotic shock has been purified by ion-exchange chromatography and isoelectric focusing. The purified enzyme (mol. wt. 4.1 x 10", S optimum 9.5, temperature optimum 37 °C) requires Ca ions, for activity and prefers unmethylated poly(D-galacturonic acid) as a substrate. Ways of releasing more of the enzyme from the cells were reported. 

Poly(D-galacturonic acid) cross-linked with epichlorohydrin has been used in the purification of polygalacturonase by affinity chromatography. ... 

Pectin Citrus peel, commercial Poly-D-galacturonic acid... 

In the course of studies on the physicochemical properties of natural polymers in aqueous solution, attention has been drawn to pectic acid, i.e. poly (a-D)galacturonic acid as a potential model of a rigid polysaccharide. 

Extensive data are given in the Uterature for the potentiometric titration of polymer acids which may be used to study the behaviour of polyelectrolyte systems under different conditions. For poly(a-D) galacturonic acid there are few data of this kind, especially in connection with the occurrence of a conformational transition induced by pH variations, or with the effect brought about by the addition or the exchange of counterions. Since for a polyacid not exhibiting a conformational transition in the course of titration, pK K denoting the apparent dissociation constant) increases monotonously with degree... 

The purpose of this study is to consider in more detail the influence of the size and nature of the counterion on the degree and extent of dissociation of poly(a-D)galacturonic acid already discussed in a previous paper [2], particularly to check the effect of screening the charges on the polyacid in the presence of different counterions. 

Commercially available poly(a-D)galacturonic acid PGA) was purchased from Fluka Chemie. To obtain an aqueous solution of the polyacid, insoluble PGA was converted to its soluble sodium salt and then percolated through a cation-exchange resin in the H-form [3]. 

It is now clear that the basic skeletons of all pectic substances consist essentially of poly-a-D-galacturonic acids the constituent units of which contain the pyranose ring and are linked glycosidically in a configuration through positions 1 and 4.s 6... 

We may return now to the polysaccharides present in the peanut for a brief consideration of the relationship of the other components present in the pectic materials to the araban constituent. All the evidence indicates that the pectic acid portion of the peanut is identical with normal pectic acid and, as was indicated in the previous section, this material, which is very stable to acid hydrolysis and possesses a high positive rotation contains a main chain which is built up of D-galacturonic acid residues of the pyranose type. If, therefore, the araban associated with the pectic acid had been derived directly from the pectic acid by decarboxylation without intermediate hydrolysis of the poly-galacturonide, the sugar residues in the araban should also be in the pyranose form. The experimental evidence shows clearly, however, that the arabinose residues in araban are furanose in type and it follows that any hypothesis concerning the direct conversion of pectic acid into the araban by decarboxylation is untenable. 

Rees (22) proposed four levels of structure for polysaccharides like pectin. Primary structure refers to the nature and mode of linkage of the component galacturonlc acids. In pectin, poly-D-galacturonate forms a regular, buckled, two-fold conformation... 

Pectic acid is poly [a-(l 4)-D-galacturonic acid]. Depending on origin,... 

---