A structure-based approach to control the size and linkage-type of sucrose derived alpha-glucans

The demand for bio-derived and biodegradable polymers and oligomers is impressively increasing due to societal and environmental concerns. Among the bio-sourced polymers, the a-glucans produced from sucrose using the glucansucrases from the family 70 of glycoside-hydrolases are quite attractive. They can display various structures, in terms of linkage type, molar mass and polydispersity. Their specific traits directly govern their physico-chemical and biological properties at the source of their potential usage in pharmaceutical, cosmetic or agro-food industries. The accessible molecular diversity is thus large and of interest to extend a-glucan applications. However, the fine control of the structures still suffers from a lack of basic knowledge in the mechanistic and structural determinants at the source of the GH70 enzyme specificity. To fill this gap, we have recently selected different glucansucrases, named DSR-OK, DRS-M and ASR. They synthesize polymers with marked structural differences in terms of size or linkage content. We have solved several 3D structures of these enzymes, unliganded or in complex with different substrates and/or products. The structural analysis of these proteins combined to mutagenesis and biochemical characterization enabled us to identify key determinants of specificity and elaborate mechanistic scenarios for both polymer elongation and linkage type formation. We will first give an overview of the molecular mechanisms involved in polymer formation and will discuss our recent advances with regard to the complexity of the occurring phenomena. We will also show how our findings can rationally serve to construct mutants and chimera leading to a broader range of bioproducts with well-defined structures. Grimaud et al., Green Chemistry, 2018, 20, 4012. Claverie et al., ACS Catalysis, 2017, 7, 7106. Molina et al., ACS Catalysis, 2019, accepte

Enzymatic glycosylation of Ellagic acid

Ellagic acid is a natural biomolecule with several biological propertiesi such as anti-oxidant activity. However the poor solubility of this compound limits its bioavailability and its potential for pharmaceutical or cosmetic application.ii It’s well-known that glycosylation can significantly improve the physicochemical and biological properties of small molecules.iii Enzymatic glycosylation of this compound would be a solution to access a more soluble ellagic acid through a sustainable and environmentally friendly process. Glucansucrases, that use sucrose as donor substrate to transfer a glucose unit, are highly promising catalysts to glycosylate high valuated biomolecules.iv Please click Additional Files below to see the full abstract

Using Glucan Water Dikinase for in vitro glucan phosphorylation

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Sucrose analogs: an attractive (bio)source for glycodiversification

Sucrose is a widespread carbohydrate in nature and is involved in many biological processes. Its natural abundance makes it a very appealing renewable raw material for the synthetic production of high-valued molecules. To further diversify the structure and the inherent properties of these molecules, the access to sucrose analogs is of utmost interest and has historically been widely explored through chemical means. Nature also offers a large panel of sucrose-scaffold derivatives, including phosphorylated or highly substituted phenylpropanoid esters amenable to transformation. Additionally, the use of microorganisms or enzymes could provide an alternative ecologically-compatible manner to diversify sucrose-scaffold derivatives to enable the synthesis of oligo- or polysaccharides, glycoconjugates or polymers that could exhibit original properties for biotechnological applications. This review covers the main biological routes to sucrose derivatives or analogs that are prevalent in nature, that can be obtained via enzymatic processes and the potential applications of such sucrose derivatives in sugar bioconversion, in particular through the engineering of substrates, enzymes or microorganisms

ProSAR: Implementation and assessment of an approach based on a genetic algorithm towards directed evolution of enzymes

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ProSAR: Implementation and assessment of an approach based on a genetic algorithm towards directed evolution of enzymes

International audienceno abstrac

GH13 amylosucrases and GH70 branching sucrases, atypical enzymes in their respective families

Amylosucrases and branching sucrases are alpha-retaining transglucosylases found in the glycoside-hydrolase families 13 and 70, respectively, of the clan GH-H. These enzymes display unique activities in their respective families. Using sucrose as substrate and without mediation of nucleotide-activated sugars, amylosucrase catalyzes the formation of an alpha-(1 -> 4) linked glucan that resembles amylose. In contrast, the recently discovered branching sucrases are unable to catalyze polymerization of glucosyl units as they are rather specific for dextran branching through alpha-(1 -> 2) or alpha-(1 -> 3) branching linkages depending on the enzyme regiospecificity. In addition, GH13 amylosucrases and GH70 branching sucrases are naturally promiscuous and can glucosylate different types of acceptor molecules including sugars, polyols, or flavonoids. Amylosucrases have been the most investigated glucansucrases, in particular to control product profiles or to successfully develop tailored alpha-transglucosylases able to glucosylate various molecules of interest, for example, chemically protected carbohydrates that are planned to enter in chemoenzymatic pathways. The structural traits of these atypical enzymes will be described and compared, and an overview of the potential of natural or engineered enzymes for glycodiversification and chemoenzymatic synthesis will be highlighted

Prediction of enzyme activity: Implementation of the ProSAR method and assessment on experimental dataset from different sources

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A new method for spectral characterization of protein families from sequence information using Fourier Transform

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