Rhamnogalacturonan-II (RG-II) is a complex polysaccharide component of pectin that is found in the primary cell walls of dicotyledonous and monocotyledonous plants and gymnosperms.[1] It is supposed to be crucial for the plant cell wall integrity. RG-II is also likely to be present in the walls of some lower plants (ferns, horsetails, and lycopods). Its global structure is conserved across vascular plants, albeit a number of variations within the RGII side chains have been observed between different plants.[2] RG-II is composed of 12 different glycosyl residues including D-rhamnose, D-apiose, D-galactose, L-galactose, Kdo, D-galacturonic acid, L-arabinose, D-xylose, and L-aceric acid, linked together by at least 21 distinct glycosidic linkages. Some resides are further modified via methylation and acetylation. It moreover supports borate mediated cross-linking between different RGII side-chain apiosyl residues. The backbone consists of a linear polymer of alpha-1,4-linked D-galactopyranosiduronic acid. RG-II can be isolated from different sources, such as apple juice and red wine.[3]

Structure of rhamnogalacturonan II in SNFG format

The gut bacterium Bacteroides thetaiotaomicron has a polysaccharide utilization locus that contains enzymes that allows deconstruction of rhamnogalacturonan-II, cleaving all but 1 of its 21 distinct glycosidic linkages.[4]

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  1. ^ O'Neill, MA; Ishii, T; Albersheim, P; Darvill, AG (2004). "Rhamnogalacturonan II: structure and function of a borate cross-linked cell wall pectic polysaccharide". Annu. Rev. Plant Biol. 55: 109–139. doi:10.1146/annurev.arplant.55.031903.141750. PMID 15377216.
  2. ^ Pabst, Martin; Fischl, Richard M.; Brecker, Lothar; Morelle, Willy; Fauland, Alexander; Köfeler, Harald; Altmann, Friedrich; Léonard, Renaud (July 2013). "Rhamnogalacturonan II structure shows variation in the side chains monosaccharide composition and methylation status within and across different plant species". The Plant Journal. 76 (1): 61–72. doi:10.1111/tpj.12271. PMID 23802881.
  3. ^ Pellerin, Patrice; Doco, Thierry; Vida, Stéphane; Williams, Pascale; Brillouet, Jean-Marc; O'Neill, Malcolm A (1996). "Structural characterization of red wine rhamnogalacturonan II". Carbohydrate Research. 290 (2): 183–97. doi:10.1016/0008-6215(96)00139-5. PMID 8823907.
  4. ^ Ndeh, Didier (2017). "Complex pectin metabolism by gut bacteria reveals novel catalytic functions". Nature. 544 (7648): 65–70. Bibcode:2017Natur.544...65N. doi:10.1038/nature21725. PMC 5388186. PMID 28329766.