Sodium polypectate

Chromatographic characterisation of hydrolysis products Hydrolysis products from sodium polypectate were analysed by thin-layer chromatography on silica gel G-60, using ethyl acetate / acetic acid / formic acid / water (9 3 1 4, by volume) as the mobile phase system. Sugars were detected with 0,2% orcinol in sulphuric add-methanol (10 90ml) [14]. 

Figure 1. Effect of 1% (w/v) pectin (pect), 1% galactose (gal), and of the simultaneous presence of 2% glucose (glu) on the production of extracellular polygalacturonase activity. Two-stages cultures were prepared as described under methods. Polygalacturonase was assayed in the culture filtrate as reducing sugar-releasing activity using sodium polypectate as a substrate.

A viscometric assay and identification of hydrolysis products were used to determine the mechanism of action of PG. An endo-PG is characterized by a strong reduction in viscosity (e.g. 50%) with a concomitantly low (e.g. 1-3%) release of reducing groups [9]. The time required for 50% decrease in viscosity of a 3.0% (w/v) sodium polypectate solution at 25°C was approximately 10 min, at which time about 1.5% of the total galacturonide bonds had been hydrolysed (data not shown). These results reveal a random mechanism of hydrolysis of sodium polypectate and the enzyme was a poly oc(l,4)-D-galacturonide glycanohydrolase (EC 3.2.1.15) or endo-PG. 

Ndi, E. E., Swanson, B. G., Barbosa-Canovas, G. V, and Luedecke, L. O. 1996. Rheology and microstructure of /6-lactoglobulin/sodium polypectate gels. J. Agric. Food Chem. 44 86-92. 

Two poly-D-galacturonases have been obtained from cultures of Botrytis cinerea. One of them (pH optimum 4.5, temperature optimum 50 °C) hydrolysed roughly 40% of the glycosidic linkages in sodium polypectate, but it did not hydrolyse oligogalacturonides of d.p. < 5, whereas the other (pH optimum 4.0, temperature optimum 45 °C) hydrolysed sodium polypectate (89%) and oligogalacturonides of d.p. 2—4. Tetranitromethane and 4-chloromercuribenzoate inhibited both activities, although cysteine reactivated the latter. 

Two extracellular poly-D-galacturonases have been isolated from culture fluids of Botrytis cinerea. One of them (mol. wt. 3.7 x 10 ) specifically hydrolysed sodium polypectate, whereas the other (mol. wt. 6.9 x 10 ) hydrolysed sodium polypectate and pectin, but was accompanied by pectinesterase activity. 

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