R. Schroder et al., Purification and characterisation of a galactoglucomannan from kiwifruit (Actinidia deliciosa), CARBOHY RES, 331(3), 2001, pp. 291-306
A galactoglucomannan (GGM) has been purified from the primary cell walls of
ripe kiwifruit. A combination of barium hydroxide precipitation, anion exc
hange- and gel-permeation chromatography gave a chemically homogeneous poly
mer with a 1:2:2 galactose-glucose-mannose ratio and a molecular weight ran
ge of 16-42 kDa. Complete hydrolysis of the polymer with endo-1,4-beta -man
nanase (EC 3.2.1.78) from Aspergillus niger gave a mixture of oligosacchari
des, three of which (II, III, IV) accounted for more than 80%, of the GGM.
Structural characterisation of these oligosaccharides and the original poly
saccharide was achieved by linkage analysis, 1D and 2D NMR spectrometry and
enzymatic hydrolysis. Oligosaccharide II beta -D-Glcp-(1 -->4)-beta -D-Man
p-(1 -->, III beta -D-Glcp-(1 -->4)[alpha -oD-Galp-(1 -->6)]-beta -D-Manp-(
1 -->, and IV beta -D-Glcp-(1 -->4)-[beta -D-Galp-(1 -->2)-alpha -D-Galp-(1
-->6)]-beta -D-Manp-(1 -->4)-beta -D-Glcp-(1 -->4)-beta -D-Manp-(l -, appe
ared in the molar ratio of 2.1:1. A trace amount of mannobiose (I) was dete
cted, indicating that some of the mannosyl residues were contiguous. It is
concluded that the predominant structural feature of kiwifruit GGM is a bac
kbone of alternating beta-(1 -->4)-linked D-glucopyranosyl and D-mannopyran
osyl residues, with approximately one third of the latter carrying side-cha
ins at O-6 of single alpha -D-Galp-(1 --> residues (50% of the branches) or
the disaccharide beta -D-Galp-(1 -->2)-alpha -D-Galp-(1 --> (50% of the br
anches), the substituted residues being separated by three or five unsubsti
tuted monosaccharide units. (C) 2001 Elsevier Science Ltd. All rights reser
ved.