Invited Lecture:
ALGAL CELL WALL POLYSACCHARIDE DEGRADING SYSTEMS: MARINE AGAROLYTIC AND ALGINOLYTIC ENZYME SYSTEMS FROM THE HETEROTROPHIC FLAVOBACTERIUM

Mirjam Czjzek 1 François Thomas 2 Etienne Rebuffet 3 Jan-Hendrik Hehemann 4 Murielle Jam 1 Gaëlle Correc 1 Tristan Barbeyron 1 Gurvan Michel 1
1UMR 7139 Marine Plants and Biomolecules, UPMC University Paris 6 and CNRS, Station Biologique de Roscoff, Roscoff
2Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA
32Department of Chemistry, Biochemistry and Biophysics, University of Gothenburg, Göteborg
4Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA
Marine algal polysaccharides differ from their terrestrial counterparts [1] and their associated enzymes usually constitute novel protein families. We have applied a knowledge-based strategy for the structural and biochemical characterization of candidate ‘hypothetical conserved proteins’ to identify new enzyme functions, missing in the metabolic pathways by which marine polysaccharides are degraded in the marine environment. The flavobacterium Zobellia galactanivorans has been isolated from the red alga D. sanguinea [2] and extensively studied for its capacity to degrade agars and carrageenans [3]. The complete genome of Z. galactanivorans has been sequenced and annotated, confirming that this marine bacterium displays a huge potential for the degradation of algal polysaccharides. To characterize new glycoside hydrolases and lyases in the Zobellia genome, we apply different strategies to identify and select relevant target-proteins: phylogenic approaches can be used to detect new subfamilies within polyspecific GH families, as exemplified by the discovery of the first porphyranases in the family GH16 [4]. Another example concerns the structural and biochemical characterization, of a new family of glycoside hydrolases typical of coastal environment, starting from a ‘putative protein with unkown function’ [5]. Using a combination of comparative genomic approaches, activity screening and crystallographic methods, we were able to assign the 1,3-a-3,6-anhydro-L-galactosidase activity to a member of the GH117 family. Several alginate lyases cluster together in operon like structures [6]. The biochemical and structural characterization of these show adapted substrate specific determinants. Several of these examples will be presented, giving insights into structural determinants that appear to relate to ‘marine specific’ features.

1. Kloareg, B., and Quatrano, R.S. (1988) Oceanogr Mar Biol Ann Rev 26: 259-315

2. Barbeyron, T., et al. (2001) Int J Syst Evol Microbiol 51: 985-997

3. Michel, G., et al. (2006) Appl Microbiol Biotechnol 71: 23-33

4. Hehemann, J.H.,et al. (2010) Nature 464: 908-912

5. Rebuffet E., et al. (2011) Environ Microbiol., 13:1253-70.

6. Thomas, F., et al (2012) Environ Microbiol. 14:2379-2394.



 




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