Pectins beet, molecular weight

This novel enzyme was the only esterase able to release acetyl from sugar beet pectin and removed about 30% of the total acetyl groups present. It also caused the release of acetyl groups from a range of other acetylated substrates, either synthetic or extracted from plants, in small amounts. PAE had an apparent molecular weight of 60 kDa and showed optimal activity at pH 5.5 and a temperature of 50 C. The enzyme is sensitive to buffer composition and requires a bivalent cation for optimal activity and stability. In purified form this enzyme proved unstable, especially in phosphate buffers. 

The first probable values for the molecular size of the native pectins from apple and sugar beet were obtained by Schneider and co-workers.71 These workers prepared the nitro- and acetyl-derivatives in order to avoid the anomalous behavior due to charge effects which occurred using the unsubstituted polysaccharides. From osmotic and viscometric measurements on the nitrate, values for the molecular weight of 30,000-100,000 were found, the constant Km in Staudinger s equation being 6(10)-4. Viscometric measurements indicated that there was little difference in size between the two derivatives. 

Table 1 Molecular weight (Mw), degree of esterification (DEf and anhydrous galacturonic acid content (AG) of the four depolymerized citrus pectin and sugar beet pectin samples investigated with respect to their emulsification properties...

Extrusion tripled the water solubility of sugar beet pulp fiber, primarily by reducing the molecular weight of pectin and hemicelluloses molecules (Ralet et ai, 1991). Ferulic acid, a phenolic acid normally associated with plant cell walls, was also recovered from the soluble sugar beet fraction. Smaller fragments may be soluble in aqueous ethanol, and thus discarded during the extraction steps common to enzymatic-gravimetric and enzymatic-chemical methods of fiber analysis. 

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