This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Carbohydrates Degradation → Polysaccharides Degradation → Carrageenan Degradation|
|Degradation/Utilization/Assimilation → Polymeric Compounds Degradation → Polysaccharides Degradation → Carrageenan Degradation|
Some taxa known to possess this pathway include : Coraliomargarita akajimensis DSM 45221 , Pseudoalteromonas carrageenovora , Pseudoalteromonas sp. AJ5 , Pseudoalteromonas sp. LL1 , Rhodopirellula baltica , Zobellia galactanivorans
Expected Taxonomic Range:
Carrageenans and carrageenoses are sulfated polysaccharides that are extracted from sea weeds belonging to the Rhodophyta (red algae), mainly from Chondrus crispus, and species from the Eucheuma and Gigartina genera. They are laid out in the cell wall at a high density and can constitute up to 50% of the algae dry mass.
The basic units of carrageenans are repeats of alternating β -1,3 linked D-galactose and α-1,4- linked D-galactose units, which are often substituted by sulfate. Carrageenans are classified according to the number and the position of sulfated ester [Matsuhiro92].
In carrageenoses the α-1,4- linked galactose units are modified by having a 3,6 - anhydro bridge. These bridges, which form a double helix during aggregation, are responsible for the gelation that is typical to these compounds. Despite this distinction, carrageenoses are often referred to as carrageenans.
The three most industrially exploited carrageenans, namely, κ-carrageenose, ι-carrageenose and λ-carrageenan, are distinguished by the presence of one, two or three ester-sulfate groups per repeating disaccharide unit respectively.
κ-carrageenose is sulfated only at position 4 of the β -1,3 linked D-galactose units.
About This Pathway
Carrageenans constitute a crucial carbon source for a number of marine bacteria. These organisms, which belong mainly to the classes Gammaproteobacteria, Flavobacteria and Sphingobacteria, degrade the cell walls of marine red algae by secreting specific glycoside hydrolases known as carrageenases.
The marine bacterium Pseudoalteromonas carrageenovora produces an endo-cleaving enzyme that attacks the (1→4)-β-D-linkages between D-galactose 4-sulfate and 3,6-anhydro-D-galactose in κ-carrageenans, producing the disaccharide neocarrabiose sulfate and the tetrasaccharide neocarratetraose 4-O-disulfate as the main products with retention of the anomeric configuration [Weigl66, McLean79]. One of the sulfate groups of the tetraose is removed by the bifunctional enzyme neocarrabiose sulfate/neotetraose disulfate 4-sulfatase, generating neocarratetraose 4-O-sulfate [McLean79a], which is cleaved by neocarratetraose 4-O-monosulfate β-hydrolase to neocarrabiose sulfate and neocarrabiose [McLean81]. Finally, the second sulfate group is then removed from neocarrabiose sulfate by neocarrabiose sulfate/neotetraose disulfate 4-sulfatase, leaving neocarrabiose as the sole product [Weigl66a].
Guibet06: Guibet M, Kervarec N, Genicot S, Chevolot Y, Helbert W (2006). "Complete assignment of 1H and 13C NMR spectra of Gigartina skottsbergii lambda-carrageenan using carrabiose oligosaccharides prepared by enzymatic hydrolysis." Carbohydr Res 341(11);1859-69. PMID: 16716278
Barbeyron94: Barbeyron T, Henrissat B, Kloareg B (1994). "The gene encoding the kappa-carrageenase of Alteromonas carrageenovora is related to beta-1,3-1,4-glucanases." Gene 139(1);105-9. PMID: 8112578
Falshaw05: Falshaw R, Furneaux RH, Stevenson DE (2005). "Structural analysis of carrageenans from the red alga, Callophyllis hombroniana Mont. Kutz (Kallymeniaceae, Rhodophyta)." Carbohydr Res 340(6);1149-58. PMID: 15797130
Michel01: Michel G, Chantalat L, Duee E, Barbeyron T, Henrissat B, Kloareg B, Dideberg O (2001). "The kappa-carrageenase of P. carrageenovora features a tunnel-shaped active site: a novel insight in the evolution of Clan-B glycoside hydrolases." Structure 9(6);513-25. PMID: 11435116
Michel99: Michel G, Barbeyron T, Flament D, Vernet T, Kloareg B, Dideberg O (1999). "Expression, purification, crystallization and preliminary x-ray analysis of the kappa-carrageenase from Pseudoalteromonas carrageenovora." Acta Crystallogr D Biol Crystallogr 55(Pt 4);918-20. PMID: 10089334
Potin95: Potin P, Richard C, Barbeyron T, Henrissat B, Gey C, Petillot Y, Forest E, Dideberg O, Rochas C, Kloareg B (1995). "Processing and hydrolytic mechanism of the cgkA-encoded kappa-carrageenase of Alteromonas carrageenovora." Eur J Biochem 228(3);971-5. PMID: 7737202
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