The sulphated-galactan hydrolases, agarases and carrageenases: structural biology and molecular evolution
Barbeyron, T.; Flament, D.; Michel, G.; Potin, Ph.; Kloareg, B. (2001). The sulphated-galactan hydrolases, agarases and carrageenases: structural biology and molecular evolution. Cah. Biol. Mar. 42(1-2): 169-183
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723; e-ISSN 2262-3094, more
Also appears in:(2001). Proceedings of the International Workshop "Current approaches in basic and applied phycology". Cahiers de Biologie Marine, 42(1-2). [S.n.]: [s.l.]. 1-185 pp., more
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| Authors | | Top |
- Barbeyron, T.
- Flament, D.
- Michel, G.
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| Abstract |
The carrageenans and agars are major cell-wall polysaccharides from red algae. These sulphated galactans are degraded by enzymes, called carrageenases and agarases that display strict substrate specifities and recognize the pattern of galactan sulphation. From a set of various marine bacteria enzymes, we have investigated the influence of ester-sulphate groups, of D/L isomery and of linkage anomery on the structure-function relationships of the specific galactan hydrolases that degrade sulphated polysaccharides. With this aim, we have cloned a representative set of sulphated-galactan hydrolase genes. The sequence analysis methods indicate that the beta-agarases and kappa- carrageenases display secondary structure similarities with members of family 16 of glycoside hydrolases. In contrast, the L-carrageenases have no structural relationships with the family-16 beta-agarases and kappa-carrageenases and they constitute a novel structural family of glycan hydrolases. As a preliminary step towards the functional analysis of these two structural families, we have overexpressed the L- and kappa-carrageenase genes in Escherichia coli and crystals from these enzymes have been obtained. Finally, an alpha-agarase, the only one galactanase known to cleave the alpha-1,3 linkage in agarose has no similarity with other glycoside hydrolases or proteins and display some interesting characteristics. To date, this enzyme is an unclassified glycoside hydrolase. |
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