Investigating the function of an arabinan utilization locus isolated from a termite gut community

Biocatalysts are essential for the development of bioprocesses efficient for plant biomass degradation. Previously, a metagenomic clone containing DNA from termite gut microbiota was pinpointed in a functional screening that revealed the presence of arabinofuranosidase activity. Subsequent genetic and bioinformatic analysis revealed that the DNA fragment belonged to a member of the genus Bacteroides and encoded 19 open reading frames (ORFs), and annotation suggested the presence of hypothetical transporter and regulator proteins and others involved in the catabolism of pentose sugar. In this respect and considering the phenotype of the metagenomic clone, it was noted that among the ORFs, there are four putative arabinose-specific glycoside hydrolases, two from family GH43 and two from GH51. In this study, a thorough bioinformatics analysis of the metagenomic clone gene cluster has been performed and the four aforementioned glycoside hydrolases have been characterized. Together, the results provide evidence that the gene cluster is a polysaccharide utilization locus dedicated to the breakdown of the arabinan component in pectin and related substrates. Characterization of the two GH43 and the two GH51 glycoside hydrolases has revealed that each of these enzymes displays specific catalytic capabilities and that when these are combined the enzymes act synergistically, increasing the efficiency of arabinan degradation

Exploration of the lignocellulotytic potential of invertebrate microbiome

International audienc

Exploration of the lignocellulotytic potential of invertebrate microbiome

International audienc

Investigating the multimodularity of a Xyn10C-like protein found in a termite gut

International audienc

Substrate specificity, regiospecificity, and processivity in glycoside hydrolase family 74

Glycoside hydrolase family 74 (GH74) is a historically important family of endo-beta-glucanases. On the basis of early reports of detectable activity on cellulose and soluble cellulose derivatives, GH74 was originally considered to be a "cellulase" family, although more recent studies have generally indicated a high specificity toward the ubiquitous plant cell wall matrix glycan xyloglucan. Previous studies have indicated that GH74 xyloglucanases differ in backbone cleavage regiospecificities and can adopt three distinct hydrolytic modes of action: exo, endo-dissociative, and endo-processive. To improve functional predictions within GH74, here we coupled in-depth biochemical characterization of 17 recombinant proteins with structural biology-based investigations in the context of a comprehensive molecular phylogeny, including all previously characterized family members. Elucidation of four new GH74 tertiary structures, as well as one distantly related dual seven-bladed beta-propeller protein from a marine bacterium, highlighted key structure-function relationships along protein evolutionary trajectories. We could define five phylogenetic groups, which delineated the mode of action and the regiospecificity of GH74 members. At the extremes, a major group of enzymes diverged to hydrolyze the backbone of xyloglucan nonspecifically with a dissociative mode of action and relaxed backbone regiospecificity. In contrast, a sister group of GH74 enzymes has evolved a large hydrophobic platform comprising 10 subsites, which facilitates processivity. Overall, the findings of our study refine our understanding of catalysis in GH74, providing a framework for future experimentation as well as for bioinformatics predictions of sequences emerging from (meta)genomic studies

Exploration of the lignocellulolytic potential of invertebrate microbiome

International audienc

Exploration of the lignocellulolytic potential of invertebrate microbiome

International audienc

Hemicellulytic potential of invertebrate microbiome for biorefinery

International audienc

Mining for lignocellulases in termite using fonctionnal metagenomics.

International audienc