Polymeric Iminosugars Improve the Activity of Carbohydrate-Processing Enzymes

Multivalent iminosugars have recently emerged as powerful tools to inhibit the activities of specific glycosidases. In this work, biocompatible dextrans were coated with iminosugars to form linear and ramified polymers with unprecedently high valencies (from 20 to 900) to probe the evolution of the multivalent inhibition as a function of ligand valency. This study led to the discovery that polyvalent iminosugars can also significantly enhance, not only inhibit, the enzymatic activity of specific glycoside-hydrolase, as observed on two galactosidases, a fucosidase, and a bacterial mannoside phosphorylase for which an impressive 70-fold activation was even reached. The concept of glycosidase activation is largely unexplored, with a unique recent example of small-molecules activators of a bacterial O-GlcNAc hydrolase. The possibility of using these polymers as “artificial enzyme effectors” may therefore open up new perspectives in therapeutics and biocatalysis

Structural analysis of the soluble exopolysaccharides produced by selected strains.

a<p>All the strains in the Table also displayed <i>eps1</i> and <i>eps2</i> clusters. None displayed <i>gtf.</i></p>b<p>The EPS concentration was determined by the anthrone sulfuric method. The number between brackets indicates the number of chromatographic peaks after gel permeation on superdex 30 column. The peak at 5500 Da was always present. The second peak, when present indicates the presence of polymers with molecular weight higher than 1 000 000 Da.</p>c<p>ND: not determined, no high molecular weight EPS produced.</p

Observation of <i>O. oeni</i> capsules by transmission electron microscopy.

<p>The black arrow indicates the place where the capsule may appear as a dark halo/layer when present. The strain <i>L. lactis</i> IL1403, which displays a thin polysaccharide pellicle as demonstrated by Chapot Chartier et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098898#pone.0098898-ChapotChartier1" target="_blank">[70]</a>, serves as a reference. Strains <i>O. oeni</i> S28 and 0607 are clearly encapsulated, while strain 0205 has no dense area beyond the peptidoglycan layer (light gray layer).</p

Protein sequence identity in <i>eps1</i> clusters.

a<p>NC: No Cazy number.</p>b<p>Identity (%) between proteins of selected strains representative of each model :<i>O. oeni</i> PSU-1 (model A) is used as a reference, and ortholog proteins of strain <i>O. oeni</i> B429 (model B) and <i>O. oeni</i> B422 (model C) are compared to <i>O. oeni</i> PSU-1 ones, except for WoaF, for which the sequence found in <i>O. oeni</i> B-429 is used as the reference. When two strains display the same model of cluster <i>eps1</i>, the identity between related proteins is higher than 98%. Abs: protein absent.</p

Genetic organization of <i>O oeni</i> chromosome regions harboring <i>dsrO</i> and <i>dsrV</i> genes.

<p>Example of strains <i>O. oeni</i> PSU-1, BAA-1163, 0607 and 277. The strain 277 also diplays a <i>dsrO</i> gene, similar to that found in <i>O. oeni</i> PSU-1.</p

Schematic representation of the <i>eps loci</i> on the chromosome of <i>O. oeni</i>.

<p>The chromosome of <i>O. oeni</i> PSU-1 is represented with its own <i>eps genes or loci</i> (black). The position of the adjacent regions of the additional <i>loci</i> found in other <i>O. oeni</i> strains are presented in gray: <i>eps1</i> and <i>eps2</i>: heteropolysaccharide clusters; <i>gtf:</i> β-glucan synthase gene; <i>it3</i> and <i>it4</i>: priming glycosyltransferase isolated genes; <i>dsrO</i> and <i>dsrV</i>: dextransucrase genes; <i>levO</i>: levansucrase gene.</p

Putative precursor biosynthetic pathways active in <i>O. oeni</i> deduced from genome analysis.

<p>The enzyme full names and the accession numbers of reference proteins are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098898#pone.0098898.s001" target="_blank">Table S1</a> (panel precurors). The solid arrows indicate the central pathways (glucose 6-P to xylulose-5-P and PEP and acetyl-CoA) and the pathways potentially active in all the strains studied, as the associated enzymes are encoded by the 50 genomes studied. The dashed arrows indicate pathways putatively active in a smaller number of strains. The EPS monomer precursors potentially available in all the strains studied are boxed in solid lines, while the precursors putatively available in a limited number of strains are boxed with dotted lines. “?” indicate metabolic steps for which no enzyme was identified from the genome analyses. <i>P: phosphate, CoA : coenzyme-A, NDP : nucleotidyl-diphosphate, CDP : cytidyl-diphosphate, UDP : uridine-diphosphate; GDP: guanosine-diphosphate, dTDP : desoxythymidine diphosphate, Glc : glucose, Fru : fructose, GlcA : glucuronic acid, Gal : galactose, Galp : galactopyranose, Galf : galactofuranose</i>, LicA: choline kinase, LicC: choline cytidyltransferase <i>LRha, L-rhamnose, GlN : glucosamine, N-Ac-Glc : N-acetyl glucosamine, N-Ac-Gal : N-acetyl-galactosamine, N-Ac-Man : N-acetyl-mannosamine, G-A-P : glyceraldehyde 3-phosphate, DHAP: dihydroxyacetone phosphate, PEP : phosphoenolpyruvate.</i></p