Induction, purification et caractérisation moléculaire d une quercétinase produite par Penicillium olsonii

Les quercétinases sont des dioxygénases à cuivre produites par différents champignons filamenteux lorsqu ils se développent en présence de flavonols. Elles appartiennent à la voie catabolique de la rutine et catalysent la décomposition de la quercétine en depside avec libération concomitante de monoxyde de carbone. Ce travail a porté sur une quercétinase produite par Penicillium olsonii. Une étude d induction, impliquant les composés phénoliques et les sucres appartenant à la voie catabolique de la rutine, a été entreprise pour comprendre la régulation de la production de l enzyme chez Penicillium olsonii. Cette étude a nécessité la mise au point préalable de la synthèse du produit de la réaction catalysée par la quercétinase, le depside. L enzyme a ensuite été purifiée et partiellement caractérisée. Enfin, une étude génétique a permis de séquencer le gène codant la quercétinase de Penicillium olsonii et d exprimer cette dernière de manière hétérologue chez Saccharomyces cerevisiae.AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

How recent knowledge on furano-specific enzymes has renewed interest for the synthesis of glycofuranosyl-containing conjugates

International audienced-Galactose in its furanose form is undoubtedly an enigma in glycosciences that has triggered numerous chemical, physical and biological studies over the last thirty years. This chapter is dedicated to show how chemists have been inspired by enzymes involved in the biosynthesis and metabolism of furanosyl-containing conjugates. The resulting molecular tools have proven to be essential for better understanding mutases, furanosyl transferases and furanosyl hydrolases, their impact, their activity and the corresponding biochemical pathways. Moreover, this chapter includes some examples highlighting the use of modern NMR techniques and of molecular biology as new tools in chemical laboratories that contributed to the elucidation of mechanism pathways and/or to the production of new biocatalysts useful for the synthesis of furanosyl-containing conjugates

Diversion of a thioglycoligase for the synthesis of 1-O-acyl arabinofuranoses

International audienceAn arabinofuranosylhydrolase from the GH51 family was transformed into an acyl transferase by mutation of the catalytic acid/base amino acid. The resulting enzyme was able to transfer carboxylic acid onto the anomeric position of arabinose with complete chemo- and stereoselectivity. A wide range of acyl α-l-arabinofuranoses was obtained with yields ranging from 25 to 83%. Using this method, ibuprofen and N-Boc phenylalanine were successfully transformed into their corresponding acyl conjugates, expanding the scope of the reaction to drugs and amino acids

Modulation of the Activity and Regioselectivity of a Glycosidase: Development of a Convenient Tool for the Synthesis of Specific Disaccharides

International audienceThe synthesis of disaccharides, particularly those containing hexofuranoside rings, requires a large number of steps by classical chemical means. The use of glycosidases can be an alternative to limit the number of steps, as they catalyze the formation of controlled glycosidic bonds starting from simple and easy to access building blocks; the main drawbacks are the yields, due to the balance between the hydrolysis and transglycosylation of these enzymes, and the enzyme-dependent regioselectivity. To improve the yield of the synthesis of β-d-galactofuranosyl-(1→X)-d-mannopyranosides catalyzed by an arabinofuranosidase, in this study we developed a strategy to mutate, then screen the catalyst, followed by a tailored molecular modeling methodology to rationalize the effects of the identified mutations. Two mutants with a 2.3 to 3.8-fold increase in transglycosylation yield were obtained, and in addition their accumulated regioisomer kinetic profiles were very different from the wild-type enzyme. Those differences were studied in silico by docking and molecular dynamics, and the methodology revealed a good predictive quality in regards with the regioisomer profiles, which is in good agreement with the experimental transglycosylation kinetics. So, by engineering CtAraf51, new biocatalysts were enabled to obtain the attractive central motif from the Leishmania lipophosphoglycan core with a higher yield and regioselectivity

Volatile Organic Compounds from a Lichen-Associated Bacterium, <i>Paenibacillus etheri</i>, Interact with Plant-Parasitic Cyst Nematodes

International audienceHealthy food is one of the major challenges to develop in this century. Plant-parasitic nematodes cause significant damage to many crops worldwide and till now, the use of chemical nematicides is the main means to control their populations. These chemical products must be replaced by more environmental-friendly control methods. Biocontrol methods seem to be one promising option, and the number of biopesticides derived from living organisms has increased in the last decades. To develop new plant protection products, we have decided to combine our skills in natural products chemistry and nematology and to focus on the lichen microecosystem as underexploited ecological niches of microorganisms. We present herein the potential of lichen-associated bacterial suspensions from Paenibacillus etheri as nematicides against the beet cyst nematode Heterodera schachtii and the potato cyst nematode Globodera pallida, in particular the effects of volatile organic compounds (VOCs) produced by the bacteria. A solid phase micro-extraction method associated to gas chromatography−mass spectrometry analysis of 14 day cultures was used to analyze these VOCs in order to identify the main produced compounds (isoamyl acetate and 2phenylethyl acetate) and to evaluate them on the nematodes

Glycoside hydrolases and glycosyltransferases from hyperthermophilic archaea: Insights on their characteristics and applications in biotechnology

International audienceHyperthermophilic Archaea colonizing unnatural habitats of extremes conditions such as volcanoes and deep-sea hydrothermal vents represent an unmeasurable bioresource for enzymes used in various industrial applications. Their enzymes show distinct structural and functional properties and are resistant to extreme conditions of temperature and pressure where their mesophilic homologs fail. In this review, we will outline carbohydrate-active enzymes (CAZymes) from hyper-thermophilic Archaea with specific focus on the two largest families, glycoside hydrolases (GHs) and glycosyltransferases (GTs). We will present the latest advances on these enzymes particularly in the light of novel accumulating data from genomics and metagenomics sequencing technologies. We will discuss the contribution of these enzymes from hyperthermophilic Archaea to industrial applications and put the emphasis on newly identifed enzymes. We will highlight their common biochemical and distinct features. Finally, we will overview the areas that remain to be explored to identify novel promising hyperthermozymes. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Improvement of the versatility of an arabinofuranosidase against galactofuranose for the synthesis of galactofuranoconjugates

International audienceGalactofuranoconjugates are rare compounds with interesting biological properties. Their syntheses by traditional approaches are however tedious. Glycosidases are nowadays often used to simplify such syntheses but the use of galactofuranosidase has not been described yet for the synthesis of galactofuranoconjugates. Interestingly CtAraf51, an α-l-arabinofuranosidase from Ruminiclostridium thermocellum, is able to use aryl- or alkyl-β-d-galactofuranosides as the substrate but with very low efficiency. To allow its use as a synthesis tool, we decided to improve the efficiency of this enzyme toward these non-natural substrates. First, we identified three residues that can contribute to unfavorable interactions with the p-nitrophenyl-β-d-galactofuranoside. After mutagenesis, two mutants have shown a catalytic efficiency four- and threefold higher than that of the wild type, respectively. These two mutants were then evaluated in the transglycosylation reaction using ethanol as a model acceptor substrate. Under these conditions one mutant was much more efficient 50% conversion was reached ten times faster than with the WT. Finally both mutants were converted into thioglycoligases in the thioligation reaction, the reaction was two times faster than with the E173A single mutant, and in the acylation reaction a fourfold increase in the initial velocity was found. The synthetic potential of the resulting mutants to synthesize various O-, S- and acyl galactofuranoconjugates was further evaluated and yields up to 82% were obtained for the synthesis of ethyl- or thiophenyl galactofuranosides and methoxybenzoic galactofuranose

Microbial community associated with the crustose lichen Rhizocarpon geographicum L. ( DC .) living on oceanic seashore: A large source of diversity revealed by using multiple isolation methods

International audienceRecently, the study of the interactions within a microcosm between hosts and their associated microbial communities drew an unprecedented interest arising from the holobiont concept. Lichens, a symbiotic association between a fungus and an alga, are redefined as complex ecosystems considering the tremendous array of associated microorganisms that satisfy this concept. The present study focuses on the diversity of the microbiota associated with the seashore located lichen Rhizocarpon geographicum, recovered by different culture-dependent methods. Samples harvested from two sites allowed the isolation and the molecular identification of 68 fungal isolates distributed in 43 phylogenetic groups, 15 bacterial isolates distributed in five taxonomic groups and three microalgae belonging to two species. Moreover, for 12 fungal isolates belonging to 10 different taxa, the genus was not described in GenBank. These fungal species have never been sequenced or described and therefore non-studied. All these findings highlight the novel and high diversity of the microflora associated with R. geographicum. While many species disappear every day, this work suggests that coastal and wild environments still contain an unrevealed variety to offer and that lichens constitute a great reservoir of new microbial taxa which can be recovered by multiplying the culture-dependent techniques

Silica-Catalysed and Highly Stereoselective Convergent and Nonconvergent Rearrangements of Menthone Enol Acetate Epoxides: Easy Access to the Four α-Hydroxymenthone Stereoisomers

International audienc

In vitro assessment of enzymatic phytate dephosphorylation during digestive process of different feeds and feed ingredients

International audienceIn vivo studies of the digestive process are long, expensive and difficult to rationalize, whereas in vitro systems may give more accessible insight into parts of this process. The purpose of this study was to show the ability of a three-step simulation of monogastric animals' digestive system to estimate phytate hydrolysis and how it is affected by feed composition. Several feed ingredients: wheat, maize, soybean meal and rapeseed meal and complete diets: a wheat-maize-soybean-mealbased diet, a maize-soybean-meal diet and a wheat-maize-rapeseed-meal diet were treated using an adaptation of a described in vitro digestion simulation system in the presence of increasing doses of phytase. A strong dependence of phytate hydrolysis on the feed ingredient used was obtained: phosphorus releases were 0.3, 0.8, 1.0 and 1.6 g/kg at 0 U/kg of phytase supplementation for maize, soybean meal, wheat and rapeseed meal respectively and 1.2, 2.9, 1.7 and 3.9 at 1000 U/kg of bacterial phytase. The efficacy of enzymatic dephosphorylation of phytate was found dependent on the ingredient, which can be partially explained by their initial content in myo-inositol phosphates. The in vitro simulation was proven a useful tool to assess enzymatic dephosphorylation of phytate under different conditions