Purification and characterisation of a galactoglucomannan from kiwifruit (Actinidia deliciosa).
A galactoglucomannan (GGM) has been purified from the primary cell walls of ripe kiwifruit. A combination of barium hydroxide precipitation, anion exchange- and gel-permeation chromatography gave a chemically homogeneous polymer with a 1:2:2 galactose-glucose-mannose ratio and a molecular weight range of 16-42 kDa. Complete hydrolysis of the polymer with endo-1,4-beta-mannanase (EC 3.2.1.78) from Aspergillus niger gave a mixture of oligosaccharides, three of which (II, III, IV) accounted for more than 80% of the GGM. Structural characterisation of these oligosaccharides and the original polysaccharide was achieved by linkage analysis, 1D and 2D NMR spectrometry and enzymatic hydrolysis. Oligosaccharide II beta-D-Glcp-(1-->4)-beta-D-Manp-(1-->, III beta-D-Glcp-(1-->4)-[alpha-D-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-(1-->, appeared in the molar ratio of 2:1:1. A trace amount of mannobiose (I) was detected, indicating that some of the mannosyl residues were contiguous. It is concluded that the predominant structural feature of kiwifruit GGM is a backbone of alternating beta-(1-->4)-linked D-glucopyranosyl and D-mannopyranosyl residues, with approximately one third of the latter carrying side-chains at 0-6 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 branches), the substituted residues being separated by three or five unsubstituted monosaccharide units.
Schröder
R
R
HortResearch, Mount Albert Research Centre, Auckland, New Zealand.
Nicolas
P
P
Vincent
S J
SJ
Fischer
M
M
Reymond
S
S
Redgwell
R J
RJ
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005638:Fruit / Q000737:chemistry*; D005690:Galactose / Q000032:analysis; D005947:Glucose / Q000032:analysis; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008351:Mannans / Q000737:chemistry* / Q000302:isolation & purification; D008358:Mannose / Q000032:analysis; D008745:Methylation; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000032:analysis
D008351:Mannans; D009844:Oligosaccharides; C443804:galactoglucomannan; C022901:(1-6)-alpha-glucomannan; D005947:Glucose; D008358:Mannose; D005690:Galactose