Arabinan

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Other names/abbreviations:

α-L-arabinofuranans Araban Arabinomannan

Material type:	Polymer
Material group:	Hetero polysaccharide, branched (Branch-on-branch) Hemicelluloses Pectic substances
Monomer(s):	L-arabinofuranose arabinopyranose D-mannose
Links:	alpha-(1-3) alpha-(1-5) alpha-(1-6) beta-(1-2)
Origin of the polymer:	Natural
CAS-Number:	11078-27-6

Structure

(→5)-α-L-arabinofuranose(1→) with random α-L-arabinofuranose(1→3) side chain [3]. The enzymatically debranched arabinan is called araban [3].

As lipoarabinomannan (LAM) the branches are (ß-Araf(1→2), (→6)-α-L-Araf(1→) or (→6)-α-Manp(1→5)-α-L-Araf(1→3) with further branching as (→2)-α-Manp(1→). The LAM is classified into two types, depending on the presence of a Manp at the nonreducing end of the oligoarabinosyl side chain [4].

Chemical properties

Behavior in solution
Soluble in water [5]. Difficult to isolate, as the α-L-arabinofuranose is extremely sensitive to acids [6]. Araban has a low solubility in water [3].

Biological properties

Molecular biology
The sidechain in the lipopolysaccharide lipoarabinomannan which is considered the major antigen of mycobacterial cell walls. LAM from Mycobacterium tuberculosis exhibit a wide variety of biological activities, like O-antigenic lipopolysaccharides, such as suppression of T lymphocyte proliferation, inhibition of γ-interferon-mediated activation of murine macrophages, immunomodulation of a large array of macrophage cytokines [1], induction of the release of tumor necrosis factor, and a generalized inhibition of antigen presentation by antigen presenting cells [5]. The arabinose-free version of LAM is not antigenic [5]. The lipoarabinomannan from Mycobacterium bovis is used as a vaccine against tuberculosis [4].


Anticoagulant activity
Sulfated arabinan from Codium latum show anticoagulant activity, 9.5 times that of heparin [2].

Physical properties

Appearance
	Physical state @ 20°C:	Solid

Bulk properties
	Molecular weight (g/mol):	Arabinan: 17,400 (LAM from Mycobacterium tuberculosis and M. bovis) [4].
	Degree of polymerization:	Araban: 50-80 [3]. Arabinan: 110 (Approximately; LAM from Mycobacterium tuberculosis and M. bovis) [4]

Occurence, isolation & synthesis

Occurence
Araninan is common in sugar beet, various seeds and roots. Occurs as side chains attached to pectate main chains through a rhamnose unit [3].

References

1: Venisse,A., Riviere,M., Vercauteren,J., Puzo,G. Structural Analysis of the Mannan Region of Lipoarabinomannan from Mycobacterium bovis BCG. Heterogeneity in Phosphorylation State
J. Biol. Chem. (1995) 270 15012-15021

2: Uehara,T., Takeshita,M., Maeda,M. Studies on Anticoagulant-Active Arabinan Sulfates from the Green Alga, Codium latum
Carbohydr. Res. (1995) 235 309-311

3: Chandrasekaran,R. X-ray Diffraction of Food Polysaccharides
Adv. Food Nutr. Res. (1998) 42 131-210

4: Venisse,A., Berjeaud,J.M., Chaurand,P., Gilleron,M., Puzo,G. Structural Features of Lipoarabinomannan from Mycobacterium bovis BCG. Determination of Molecular Mass by Laser Desorption Mass Spectrometry
J. Biol. Chem. (1993) 268 12401-12411

5: Chatterjee,D., Bozic,C.M., McNeil,M., Brennan,P.J. Structural Features of the Arabinan Component of the Lipoarabinomannan of Mycobacterium tuberculosis
J. Biol. Chem. (1991) 266 9652-9660

6: Heredia,A., Jiménez,A., Guillén,R. Composition of Plant Cell Walls
Z. Lebensm. Unters. Forsch. (1995) 200 24-31

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© Michael Pilgaard
Created: March 4, 2008