STRUCTURAL CHARACTERIZATION OF GALACTOGLUCOMANNAN SECRETED BY SUSPENSION-CULTURED CELLS OF NICOTIANA-PLUMBAGINIFOLIA

Galactoglucomannan (GGM) from cultures of Nicotiana plumbaginifolia ha s Man:Glc:Gal:Ara:Xyl in 1.0:1.1:1.0:0.1:0.04 ratio. Linkage analysis contained 4- and 4,6-Manp, 4-Glcp, terminal Galp and 2-Galp, small amo unts and terminal Arap and terminal Xylp, and similar to 0.03 mol acet yl per mol of glucosyl residue. Treatment with alpha- and beta-D-galac tosidases showed that the majority of the side-chains were either sing le Galp-alpha-(1 --> residues or the disaccharide Galp-beta-(1 --> 2)- Galp-alpha-(1 --> linked to O-6 of the 4-Manp residues of the glucoman nan backbone. Analysis of the oligosaccharides generated by endo-(1 -- > 4)-beta-mannanase digestion confirmed that the GGM comprises a backb one of predominantly alternating --> 4)-D-Manp-beta-(1 --> and --> Lt) -D-Glcp-beta-(1 --> branched at O-6 of 65% of the 4-Manp residues. The major oligosaccharide identified was D-Glcp-beta-(1 --> 4)-[D-Galp-be ta-(1 --> 2)-D-Galp-alpha-(1 --> 6)]-D-Manp-beta-(1 --> 4)-D-Glcp-beta -(I --> 4)-[D-Galp-alpha-(1 --> 6)]-D-Manp-beta-(1 --> (27%), and most of the other oligosaccharides produced in significant quantities were based on this structure. (C) 1997 Elsevier Science Ltd.