PROTOPECTINASE-T - A RHAMNOGALACTURONASE ABLE TO SOLUBILIZE PROTOPECTIN FROM SUGAR-BEET

Protopectinase-T (PPase-T), isolated from the culture broth of Trametes sanguinea, was able to release pectic substances from sugar beet by degrading rhamnogalacturonan. The smallest polysaccharide (SPS) that can serve as a substrate for PPase-T was prepared from sugar beet pulp by extraction with NaOH and digestion with alpha-L-arabinofuranosidase, alpha-L-arabinase, and beta-(1 --> 4)-D-galactanase. The reaction products of SPS with PPase-T were isolated by chromatography on DEAE-Toyopearl 650M and Toyopearl HW40-S columns, and analyzed by labeling the reducing ends with [H-3]NaBH4 and by C-13 NMR spectroscopy. The results indicated that PPase-T cleaved gal actopyranosyluronic-rhamnopyranosyl linkages in SPS. Moreover, it was confirmed that the chemical structure of SPS contains a backbone based on units of [--> 4)-alpha-D-Gal pA-(1 --> 2)-alpha-L-Rhap-(1 -->].