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Arbuscular mycorrhiza (AM) is a root endosymbiosis between plants and glomeromycete fungi. It is the most widespread terrestrial plant symbiosis, improving plant uptake of water and mineral nutrients. Yet, despite its crucial role in land ecosystems, molecular mechanisms leading to its formation are just beginning to be unravelled. Recent evidence suggests that AM fungi produce diffusible symbiotic signals. Here we show that Glomus intraradices secretes symbiotic signals that are a mixture of sulphated and non-sulphated simple lipochitooligosaccharides (LCOs), which stimulate formation of AM in plant species of diverse families (Fabaceae, Asteraceae and Umbelliferae). In the legume Medicago truncatula these signals stimulate root growth and branching by the symbiotic DMI signalling pathway. These findings provide a better understanding of the evolution of signalling mechanisms involved in plant root endosymbioses and will greatly facilitate their molecular dissection. They also open the way to using these natural and very active molecules in agriculture., Arbuscular mycorrhiza (AM) is a root endosymbiosis between fungi of the ancient phylum Glomeromycota and terrestrial plants. AM is formed by 70-90% of land plant species, improving the uptake of [...]

Endoglucanase Ce16A from Thermobifida fusca hydrolyzes the beta-1,4 linkages in cellulose at accessible points along the polymer. The structure of the catalytic domain of Ce16A from T. fusca in complex with a nonhydrolysable structure analogue that acts as an inhibitor, methylcellobiosyl-4-thiobeta-cellobioside is determined to 1.5-angstrom resolution.

Research has been conducted on the glucoamylase 1 from Aspergillus niger. Results indicate that the O-glycosylated peptide that connects the catalytic and the starch-binding domains have been substituted by the equivalent glucoamylase segments encoding amino acid residues.

Research involving efficient chemoenzymatic synthesis of a number of regioselectively modified beta(1 - 4)-oligo- and -polysaccharides is presented. The advantages of a multi-disciplinary approach for the design of new tools in organic synthesis is highlighted.

Research was conducted to investigate the binding to glucoamylase 1 from Aspergillus niger (GA1) of a series of four synthetic heterobidentate ligands of acarbose and beta-cyclodextrin (beta-CD) linked together using isothermal titration calorimetry. Results indicate that the bidentate ligands bind to both the catalytic domain and the starch-binding domain. Findings also suggest that the catalytic and starch-binding sites are in close proximity in solution and suggest considerable flexibility of the linker region.

A study was conducted to characterize the crystal structure of inactive CGTase mutant Glu257->Ala complexed with a beta-cyclodextrin derivative. Nine subsites for glucosyl units were postulated from kinetic studies with CGTase while a unifying nomenclature for oligosaccharide-binding subsites in proteins was proposed. Results indicated a distorted beta-CD ligated to CGTase from symmetrical conformations.

The structure of Fusarium oxysporum endonuclease I (EG I), a cellulase from glycosyl hydrolase family 7, complexed to a nonhydrolyzable thiooligosaccharide substrate analogue, was determined by X-ray crystallography at a resolution of 2.7 angstroms. There were three glucosyl units of the inhibitor, consistent with the known number of sugar-binding subsites. The pyranose ring at the point of potential enzymatic cleavage was clearly distorted from the standard 4C1 chair as was previously proposed for beta-retaining enzymes by Philips.

Myrosinase, a glucosidase which hydrolyzes a variety of plant 1-thio-beta-D-glucosides, was investigated to compare the mechanism of enzymatic cleavage of S- against O-glycosidic bonds. Findings revealed that myrosinase inhibition by 2-deoxy-2-fluoroglucotropaeolin occurs through the accumulation of a long-life glucosyl-enzyme intermediate and that the catalytic machinery of the enzyme is composed of only one catalytic residue, a nucleophilic glutamate, while the acid catalyst residue found in the corresponding O-glucosidases is absent.