Structural characterisation of galactoglucomannan secreted by suspension-cultured cells of Nicotiana plumbaginifolia

Galactoglucomannan (GGM) from cultures of Nicotiana plumbaginifolia has 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 amounts and terminal Arap and terminal Xylp, and ∼ 0.03 mol acetyl per mol of glucosyl residue. Treatment with α- and β-d-galac- tosidases showed that the majority of the side-chains were either single Galp-α-(1 → residues or the disaccharide Galp-β-(1 → 2)- Galp-α-(1 → linked to O-6 of the 4-Manp residues of the glucomannan backbone. Analysis of the oligosaccharides generated by endo- (1 → 4)-β-mannanase digestion confirmed that the GGM comprises a backbone of predominantly alternating → 4)-d-Man p-β-(1 → and →4)- d-Glc p-β-(1 → branched at O-6 of 65% of the 4-Manp residues. The major oligosaccharide identified was dGlep-β-(1 → 4)- [d-Gal p-β-(1 → 2)-d-Gal p-α-(1 → 6)]-d-Man p- β-(1 → 4)-d-Glc p-β-(1 → 4)-[ d-Gal p-α-(1 → 6)]-d- Man p-β-(1 → (27%), and most of the other oligosaccharides produced in significant quantities were based on this structure. The structure of GGM isolated from suspension cultures of Nicotiana plumbaginifolia has been determined using a combination of chemical, enzymic and physical techniques. Analysis of oligosaccharide was: D-Glc p-β-(1 → 4)-[D-Gal p-β-(1 → 2)-D-Gal p-α-(1 → 6)]-D-Man p-β-(1 → 4)-D-Glc p-β-(1 → 4)-[D-Gal p-α-(1 →6)]-D-Man p-β-(1 →