THE MOLECULAR CHARACTERIZATION OF THE POLYSACCHARIDE GUM FROM ACACIA-SENEGAL

Gum arabic (Acacia senegal gum) was fractionated by hydrophobic interaction chromatography on Phenyl-Sepharose CL-4B and yielded four fractions of similar carbohydrate composition, whilst differing in protein content, amino acid composition, and molecular mass distribution. All four fractions interacted with an array of anti-arabinogalactan-protein (AGP) monoclonal antibodies via anti-carbohydrate epitopes and were precipitated by Yariv's reagent, suggesting that they were all AGPs. Further characterisation using SDS-PAGE and Western blotting showed that all fractions contained proteins of molecular mass 30000-45000 with at least one protein unique to each fraction. The fractions were subjected to enzymatic (with pronase) and alkaline hydrolysis, and the molecular mass distribution of the products was monitored by gel permeation chromatography. The fractions showed various degrees of resistance to hydrolysis, thus illustrating differences in their macromolecular structure.