Nwh. Cheetham et al., STRUCTURE OF THE PRINCIPAL NONSTARCH POLYSACCHARIDE FROM THE COTYLEDONS OF LUPINUS-ANGUSTIFOLIUS (CULTIVAR GUNGURRU), Carbohydrate polymers, 22(1), 1993, pp. 37-47
Methylation analysis, selective enzymolysis (O-glycosidases) and chemi
cal degradation showed that the principal non-starch polysaccharide (N
SP) in a 2% disodium ethylenediamine-tetraacetate (EDTA) extract (puri
fied by ethanol precipitation) of lupin cotyledons (Lupinus angustifol
ius cultivar Gungurru) has the backbone sequence of [-->4)-alpha-D-Gal
pA-(1-->2)-beta-L-Rhap-(1-->]. Side chains mainly consist of linear (1
-->4)-beta-D-Galp residues and shorter, highly branched (1-->5)-alpha-
L-Araf residues are attached to the C-4 position of the rhamnosyl resi
dues in the backbone. Some terminal beta-D-Xylp residues are linked to
the galacturonosyl residues. H-1 and C-13-NMR spectroscopy support th
e proposed partial structure of the in EDTA-soluble NSP, which has a s
ugar composition and gylcosidic linkages typical of those found in pri
mary cell walls of dicots. The high proportion of neutral sugars, the
almost equal ratio of galacturonic acid to rhamnose, with most of the
latter substituted at the C-4 position, the low degree of branching of
the (1-->4)-linked galactan, and highly branched (1-->5)-linked arabi
nosyl residues are the characteristic features of the lupin cotyledon
pectic polysaccharides.