Structure-immunomodulating activity relationships of a pectic arabinogalactan from Vernonia kotschyana Sch. Bip. ex Walp.
Structure and immunological characteristics of the pectic arabinogalactan Vk2a (previously reported as Vk100A2a) from the roots of Vernonia kotschyana Sch. Bip. ex Walp. were investigated after enzymatic digestion of the galacturonan moiety and the side chains of the rhamnogalacturonan structure of Vk2a. endo-alpha-D-(1-->4)-Polygalacturonase digestion released the high molecular weight 'hairy region' (Vk2a-HR) and oligogalacturonides. Vk2a-HR consisted of GalA (4-linked) and Rha (2- or 2,4-linked) in a 1:1 ratio, with 60% of Rha branched at C-4. The Rha located in the rhamnogalacturonan core was branched randomly by Gal units. Vk2a-HR was rich in neutral sugars such as Araf 5- (12.2%) and 3,5-substituted (12.8%) and terminally- (14.1%) linked and Gal 4- (13.0%), 3- (0.9%), 6- (2.2%) and 3,6- (1.1%) substituted. Arabinans with chain lengths up to 11 units were identified. Araf residues were attached to C-3 of alpha-L-(1-->5)-Araf chains and to C-4 of Gal residues. Single Gal units and chains of beta-D-(1-->6)-linked galacto di- to penta-saccharides were attached to a beta-D-(1-->3)-galactan core. All the enzyme resistant fractions expressed potent complement fixation and induction of B-cell mitogenic activity, and the present study indicates that there may be several and possibly structurally different active sites involved in the bioactivity of Vk2a. The bioactive sites may be located both in the more peripheral parts of the molecule but also in the inner core of the 'hairy region' or in larger enzyme-resistant chains.
Department of Pharmacognosy, School of Pharmacy, University of Oslo, PO Box 1068, Blindern, 0316 Oslo, Norway. c.s.nergard@farmasi.uio.no
Cecilie Sogn
CS
Nergard
Hiroaki
H
Kiyohara
James C
JC
Reynolds
Jane E
JE
Thomas-Oates
Tsukasa
T
Matsumoto
Haruki
H
Yamada
Terje E
TE
Michaelsen
Drissa
D
Diallo
Berit Smestad
BS
Paulsen
D000818:Animals; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002241:Carbohydrates / Q000737:chemistry; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003165:Complement System Proteins / Q000737:chemistry; D004912:Erythrocytes / Q000378:metabolism; D005685:Galactans / Q000737:chemistry*; D005690:Galactose / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007477:Ions; D013058:Mass Spectrometry; D008745:Methylation; D051379:Mice; D008809:Mice, Inbred C3H; D008934:Mitogens; D009844:Oligosaccharides / Q000737:chemistry; D010368:Pectins / Q000737:chemistry*; D018517:Plant Roots / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry; D012756:Sheep; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013329:Structure-Activity Relationship
D002241:Carbohydrates; D005685:Galactans; D007477:Ions; D008934:Mitogens; D009844:Oligosaccharides; D011134:Polysaccharides; D010368:Pectins; D003165:Complement System Proteins; C005653:arabinogalactan; C003181:polygalacturonic acid; D005690:Galactose