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Arabinogalactan, also known as galactoarabinan, larch arabinogalactan, and larch gum, is a biopolymer consisting of arabinose and galactose monosaccharides. Two classes of arabinogalactans are found in nature: plant arabinogalactan and microbial arabinogalactan. In plants, it is a major component of many gums, including gum arabic and gum ghatti. It is often found attached to proteins, and the resulting arabinogalactan protein (AGP) functions as both an intercellular signaling molecule and a glue to seal plant wounds.[1]
The microbial arabinogalactan is a major structural component of the mycobacterial cell wall.[2][3] Both the arabinose and galactose exist solely in the furanose configuration. The galactan portion of microbial arabinogalactan is linear, consisting of approximately 30 units with alternating β-(1-5) and β-(1-6) glycosidic linkages. The arabinan chain, which consists of about 30 residues,[4] is attached at three branch points within the galactan chain, believed to be at residues 8, 10 and 12.[5] The arabinan portion of the polymer is a complex branched structure, usually capped with mycolic acids; the arabinan glycosidic linkages are α-(1-3), α-(1-5), and β-(1-2).
The mycobacterial arabinogalactan is recognized by a putative immune lectin intelectin present in chordates.[6]
- ^ Nothnagel EA, Bacic A, Clarke AE (2000). Cell and developmental biology of arabinogalactan-proteins. Kluwer Academic/Plenum Publishers. ISBN 978-0-306-46469-0.
- ^ Esko, Jeffrey D.; Tamara L. Doering; Christian R.H. Raetz (2008). in Essentials of Glycobiology. Cold Spring Harbor Press. pp. Ch. 20. ISBN 9780879697709.
- ^ Bhamidi S (2009). "Mycobacterial Cell Wall Arabinogalactan". Bacterial Polysaccharides: Current Innovations and Future Trends. Caister Academic Press. ISBN 978-1-904455-45-5.
- ^ Bhamidi, S.; Scherman, M. S.; Rithner, C. D.; Prenni, J. E.; Chatterjee, D.; Khoo, K.-H.; McNeil, M. R. (2008). "The Identification and Location of Succinyl Residues and the Characterization of the Interior Arabinan Region Allow for a Model of the Complete Primary Structure of Mycobacterium tuberculosis Mycolyl Arabinogalactan". Journal of Biological Chemistry. 283 (19): 12992–13000. doi:10.1074/jbc.M800222200. ISSN 0021-9258. PMC 2442352. PMID 18303028.
- ^ Alderwick, L. J.; Radmacher, E.; Seidel, M.; Gande, R.; Hitchen, P. G.; Morris, H. R.; Dell, A.; Sahm, H.; Eggeling, L.; Besra, G. S. (2005). "Deletion of Cg-emb in Corynebacterianeae Leads to a Novel Truncated Cell Wall Arabinogalactan, whereas Inactivation of Cg-ubiA Results in an Arabinan-deficient Mutant with a Cell Wall Galactan Core". Journal of Biological Chemistry. 280 (37): 32362–32371. doi:10.1074/jbc.M506339200. ISSN 0021-9258. PMID 16040600.
- ^ Tsuji, S.; Uehori, J.; Matsumoto, M.; Suzuki, Y.; Matsuhisa, A.; Toyoshima, K.; Seya, T. (19 April 2001). "Human Intelectin Is a Novel Soluble Lectin That Recognizes Galactofuranose in Carbohydrate Chains of Bacterial Cell Wall". Journal of Biological Chemistry. 276 (26): 23456–23463. doi:10.1074/jbc.M103162200. PMID 11313366.