Enzymic hydrolysis of the “hairy” fragments of sugar-beet pectins

• Published in: Carbohydrate research 1989-07, Vol.190 (1), p.97-108
• Main Authors: Guillon, Fabienne, Thibault, Jean-François, Rombouts, Frank M., Voragen, Alfons G.J., Pilnik, Walter
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Carbohydrates; Chemical Sciences; Fundamental and applied biological sciences. Psychology; Other biological molecules; Polymers
• ISSN: 0008-6215; 1873-426X; 0008-6215
• DOI: 10.1016/0008-6215(89)84150-3

The “hairy” fragments of acid-soluble (HP) and alkali-soluble (OHP) beet pectins have been treated with an arabinofuranosidase, an endoarabinanase, a β- d-galactosidase, and an endogalactanase from Aspergillus niger separately, in sequence, in combination, and prior to mild hydrolysis by 0.05 m trifluoroacetic acid. The products were analysed by h.p.l.c. and by gel-permeation chromatography on Bio-Gel P-2 and Sepharose CL-6B. The side-chains occur as branched structures attached to the rhamnogalacturonan backbone. They consist mainly of (1→5)-linked α-arabinans with branches attached to positions 3 randomly distributed along the main core, (1→4)-linked β-galactans of low d.p., and highly branched (1→3,6)-linked galactans. Of the feruloyl groups, 20–30% are carried by the arabinans and are probably responsible for their limited degradation by arabinofuranosidase. The remaining feruloyl groups are attached to the galactose residues and may contribute to the low activity of the galactanases. Some of the feruloyl groups and part of the galactose are not released by a more drastic treatment by acid. A tentative structure for the “hairy” fragments from sugar-beet pectins is presented.