Reaction: Endohydrolysis of (1→4)-β-D-linkages between D-galactose 4-sulfate and 3,6-anhydro-D-galactose-2-sulfate in ι-carrageenans
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Glossary: In the field of oligosaccharides derived from agarose, carrageenans, etc., in which alternate residues are 3,6-anhydro sugars, the prefix 'neo' designates an oligosaccharide whose non-reducing end is the anhydro sugar, and the absence of this prefix means that it is not.
ι-neocarrabiose = 3,6-anhydro-2-O-sulfo-α-D-galactopyranosyl-(1→3)-4-O-sulfo-D-galactose
ι-carrabiose = 4-O-sulfo-β-D-galactopyranosyl-(1→4)-3,6-anhydro-2-O-sulfo-D-galactose
Systematic name: ι-carrageenan 4-β-D-glycanohydrolase (configuration-inverting)
Comments: The main products of hydrolysis are ι-neocarratetraose sulfate and ι-neocarrahexaose sulfate. ι-Neocarraoctaose is the shortest substrate oligomer that can be cleaved. Unlike EC 22.214.171.124, β-agarase and EC 126.96.36.199, κ-carrageenase, this enzyme proceeds with inversion of the anomeric configuration. ι-Carrageenan differs from κ-carrageenan by possessing a sulfo group on O-2 of the 3,6-anhydro-D-galactose residues, in addition to that present in the κ-compound on O-4 of the D-galactose residues.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
1. Barbeyron, T., Michel, G., Potin, P., Henrissat, B. and Kloareg, B. ι-Carrageenases constitute a novel family of glycoside hydrolases, unrelated to that of κ-carrageenases. J. Biol. Chem. 275 (2000) 35499-35505. [PMID: 10934194]
2. Michel, G., Chantalat, L., Fanchon, E., Henrissat, B., Kloareg, B. and Dideberg, O. The ι-carrageenase of Alteromonas fortis. A β-helix fold-containing enzyme for the degradation of a highly polyanionic polysaccharide. J. Biol. Chem. 276 (2001) 40202-40209. [PMID: 11493601]
3. Michel, G., Helbert, W., Kahn, R., Dideberg, O. and Kloareg, B. The structural bases of the processive degradation of ι-carrageenan, a main cell wall polysaccharide of red algae. J. Mol. Biol. 334 (2003) 421-433. [PMID: 14623184]