Polygalacturonic acids, hydrolysis

The source materials were commercial pectins apple A30 and citrus pectin C73 kindly supplied by Unipectine (France) and Copenhagen Pectin Factory (Denmark) respectively. Polygalacturonic acid samples (named SR) were obtained by acid hydrolysis of a fully de-esterified citrus pectin as previously described [24]. Citrus pectins with different degree of esterification (DE) were obtained by controlled acid de-esterification [8]. 

A. tubingensis strain NW756 was cultivated for 55 h at 30 C in minimal medium according to Pontecorvo et al [1] supplemented with yeast extract (2g/l) and 10 g/1 endo-PG II digested polygalacturonic acid (PGA). Complete hydrolysis of PGA by endo-PG II resulted in a mixture of mono, di and trigalacturonate [2]. Four subsequent colunm chromatographic steps were used for purification of the enzyme for which the data are summarized in Table 1. 

Much of the confusion in pectic enzyme terminology was clarified by Demain and PhaflF in 1957 12) and Deuel and Stutz in 1958 11). Their classification of depolymerases was based on the substrate attacked (pectin m. non-esterified polygalacturonic acid), the mode of attack (random or endo attack vs. terminal or exo attack), and the optimal pH for enzyme activity. However it was assumed that hydrolysis was the... 

Polygalacturonic acid has been hydrolyzed by the enzyme pectinase in the preparation of D-galacturonic acid. When enzymatic hydrolysis of a polyuronide is possible, it is very useful since there is little decomposition of the products by this method. In addition it gives valuable information as to the type of glycosidic linkage present. 

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