Structural and biochemical characterization of the β-N-acetylglucosaminidase from Thermotoga maritima: toward rationalization of mechanistic knowledge in the GH73 family.

Members of the GH73 glycosidase family cleave the β-1,4-glycosidic bond between the N-acetylglucosaminyl (GlcNAc) and N-acetylmuramyl (MurNAc) moieties in bacterial peptidoglycan. A catalytic mechanism has been proposed for members FlgJ, Auto, AcmA and Atl(WM) and the structural analysis of FlgJ and Auto revealed a conserved α/β fold reminiscent of the distantly related GH23 lysozyme. Comparison of the active site residues reveals variability in the nature of the catalytic general base suggesting two distinct catalytic mechanisms: an inverting mechanism involving two distant glutamate residues and a substrate-assisted mechanism involving anchimeric assistance by the C2-acetamido group of the GlcNAc moiety.

Mutations inducing an active-site aperture in Rhizobium sp. sucrose isomerase confer hydrolytic activity.

Sucrose isomerase is an enzyme that catalyzes the production of sucrose isomers of high biotechnological and pharmaceutical interest. Owing to the complexity of the chemical synthesis of these isomers, isomaltulose and trehalulose, enzymatic conversion remains the preferred method for obtaining these products. Depending on the microbial source, the ratio of the sucrose-isomer products varies significantly.

beta-Glycosyl azides as substrates for alpha-glycosynthases: preparation of efficient alpha-L-fucosynthases.

Fucose-containing oligosaccharides play a central role in physio-pathological events, and fucosylated oligosaccharides have interesting potential applications in biomedicine. No methods for the large-scale production of oligosaccharides are currently available, but the chemo-enzymatic approach is very promising. Glycosynthases, mutated glycosidases that synthesize oligosaccharides in high yields, have been demonstrated to be an interesting alternative.

Nuclear receptor ligand-binding domains: reduction of helix H12 dynamics to favour crystallization.

Crystallization trials of the human retinoid X receptor alpha ligand-binding domain (RXRalpha LBD) in complex with various ligands have been carried out. Using fluorescence anisotropy, it has been found that when compared with agonists these small-molecule effectors enhance the dynamics of the RXRalpha LBD C-terminal helix H12. In some cases, the mobility of this helix could be dramatically reduced by the addition of a 13-residue co-activator fragment (CoA).