Some preliminary results on the action of rhamnogalacturonase on rhamnogalacturonan oligosaccharides from beet pulp.

Sugar-beet pulp was saponified and then hydrolysed with 0.1 M HCl at 80 degrees C for 72 h, and a rhamnogalacturonan fraction was isolated by ion-exchange chromatography on AG 1X8 resin. Four individual oligomers, and a mixture of oligomers with higher degrees of polymerization, were obtained by chromatography on BioGel P-4. They all presented the alpha-D-GalAp-(1[-->2)-alpha-L-Rhap-(1-->4)-alpha-D-GalAp -(1]n-->2)-L-Rhap structure (with n > or = 2) The five fractions were submitted to hydrolysis with rhamnogalacturonase. The enzyme was active on oligomers with degrees of polymerization > or = 10, and gave as main products alpha-L-Rhap-(1-->4)-alpha-D-GalAp-(1-->2)-alpha-L-Rhap++ +(1-->4)-D-GalAp and alpha-D-GalAp-(1--2)-alpha-L-Rhap-(1-->4)-alpha-D-GalAp++ +-(1-->2)-alpha-L-Rhap- 1-->4)-D-GalAp.