Relationship between structure and activity of the "ramified" region in anti-complementary pectic polysaccharides...

One of the anti-complementary pectic polysaccharides (AR-2IIa) isolated from the root of Angelica acutiloba Kitagawa gives the "ramified" region (PG-1a,rhamnogalacturonan with neutral side-chains) in addition to oligogalacturonides on digestion with endo-alpha-D-(1--4)-polygalacturonase. When the neutral side-chains in PG-1a were digested with both exo-alpha-L-arabinofuranosidase and exo-beta-D-galactosidase, approximately 70% of the arabinosyl chains and approximately 30% of the galactosyl chains were released. The resistant product E-PG-1a had the same anti-complementary activity as PG-1a. E-PG-1a gave long (d.p. greater than or equal to 5) and short (d.p. less than or equal to 4) neutral galactosyl chains after degradation of the GalA moiety by base-catalysed beta-elimination in the presence of sodium borodeuteride followed with lithium-mediated degradation. Methylation analysis showed that the long galactosyl chains consisted mainly of terminal, 6-linked and 3,6-disubstituted Gal, and that the short chains were rich in 6-linked Gal. Degradation of the GalA moieties in PG-1a markedly decreased the anti-complementary activity, but the long and short galactosyl chains still expressed approximately 50 and approximately 20%, respectively, of the anti-complementary activity of E-PG-1a.