Characterization of taste compounds: chemical structures and sensory properties

Characterization of taste compounds: chemical structures and sensory properties

Characterization of rat glutathione transferases in olfactory epithelium and mucus

International audience; The olfactory epithelium is continuously exposed to exogenous chemicals, including odorants. During the past decade, the enzymes surrounding the olfactory receptors have been shown to make an important contribution to the process of olfaction. Mammalian xenobiotic metabolizing enzymes, such as cytochrome P450, esterases and glutathione transferases (GSTs), have been shown to participate in odorant clearance from the olfactory receptor environment, consequently contributing to the maintenance of sensitivity toward odorants. GSTs have previously been shown to be involved in numerous physiological processes, including detoxification, steroid hormone biosynthesis, and am…

Oral enzymatic detoxification system: Insights obtained from proteome analysis to understand its potential impact on aroma metabolization

The oral cavity is an entry path into the body, enabling the intake of nutrients but also leading to the ingestion of harmful substances. Thus, saliva and oral tissues contain enzyme systems that enable the early neutralization of xenobiotics as soon as they enter the body. Based on recently published oral proteomic data from several research groups, this review identifies and compiles the primary detoxification enzymes (also known as xenobiotic-metabolizing enzymes) present in saliva and the oral epithelium. The functions and the metabolic activity of these enzymes are presented. Then, the activity of these enzymes in saliva, which is an extracellular fluid, is discussed with regard to the…

Engineering the sweet-tasting protein brazzein: analysis the effects on stability and sensory profile

International audience

Engineering the full sequence space of the sweet-tasting protein brazzein

International audience

Effect of high pressure on the antimicrobial activity and secondary structure of the bacteriocin nisin

International audience; Effect of high pressure (HP) treatment on the antimicrobial properties and the structure of nisin was evaluated. Nisin solutions at pH 2.8 or 6.1 were treated by HP at 500 MPa – 10 min – 20 °C and their antimicrobial potency was determined. It appeared that HP clearly impacted the antimicrobial activity of nisin, with respective activity loss of 22.5% and 49.9% at pH 2.8 and 6.1. Structural analysis of nisin by circular dichroism and Fourier transform-infrared spectroscopies revealed that the decrease of nisin antimicrobial activity was likely due to the unfolding of the protein induced by HP. A loss of nisin β-turns structure, particularly significant at neutral pH,…

Lipoproteins LDL versus HDL as nanocarriers to target either cancer cells or macrophages

free open access article 31 p.; International audience; In this work, we have explored natural unmodified low- and high-density lipoproteins (LDL and HDL) as selective delivery vectors in colorectal cancer therapy. We show in vitro in cultured cells and in vivo (NanoSPECT/CT) in the CT-26 mice colorectal cancer model that LDLs are mainly taken up by cancer cells, while HDLs are preferentially taken up by macrophages. We loaded LDLs with cisplatin and HDLs with the heat shock protein-70 inhibitor AC1LINNC, turning them into a pair of “Trojan horses” delivering drugs selectively to their target cells as demonstrated in vitro in human colorectal cancer cells and macrophages, and in vivo. Coupl…

Salivary redox status: a key parameter involved in the release and perception of sensory stimuli in human

International audience

Plant polyphenols, chemoreception, taste receptors and taste management

International audience; Purpose of review Polyphenols display beneficial health effects through chemopreventive actions on numerous chronic diseases including cancers, metabolic disorders, reproductive disorders and eating behaviour disorders. According to the principle of chemoreception, polyphenols bind cellular targets capable of accepting their stereochemistry, namely metabolizing enzymes and protein receptors, including taste receptors. The extraoral expression of taste receptors and their pharmacological interest in terms of novel drug therapies open up new perspectives on the potential use of these compounds and their interactions with other chemicals in cells. These new perspectives…

Sweeteners and sweetness enhancers

indexation en cours; PURPOSE OF REVIEW: The current review summarizes and discusses current knowledge on sweeteners and sweetness enhancers. RECENT FINDINGS: The perception of sweet taste is mediated by the type 1 taste receptor 2 (T1R2)/type 1 taste receptor 3 (T1R3) receptor, which is expressed in the oral cavity, where it provides input on the caloric and macronutrient contents of ingested food. This receptor recognizes all the compounds (natural or artificial) perceived as sweet by people. Sweeteners are highly chemically diverse including natural sugars, sugar alcohols, natural and synthetic sweeteners, and sweet-tasting proteins. This single receptor is also the target for developing …

The Recent Development of a Sweet-Tasting Brazzein and its Potential Industrial Applications

International audience; Brazzein is a small heat- and pH-stable sweet-tasting protein isolated from the West African plant, Pentadiplandra brazzeana. Brazzein combines a highly sweet potency, a long history of human consumption, and a remarkable stability, giving it great potential as a natural sweetener. Due to the difficulties of obtaining brazzein from its natural source, several efforts have been made to express brazzein using various heterologous expression systems. This chapter describes the biochemical, structural, sensory, and physiological properties of brazzein. We will summarize the current knowledge of the structure-activity relationship of brazzein. The biotechnological product…

Macrophage-induced reactive oxygen species promote myometrial contraction and labor-associated mechanisms

AbstractAt labor, the myometrium is infiltrated by a massive influx of macrophages that secrete high levels of pro-inflammatory cytokines inducing the expression of specific labor-associated markers. However, the interactions between myocytes and macrophages and the role of macrophages in the myometrium at labor remain to be elucidated. In this work, we studied the role of myometrium-infiltrated macrophages and their interaction with myocytes in lipopolysaccharide-induced preterm labor. A co-culture model of human primary myometrial cells and macrophages was developed and validated. Collagen lattices were used to evaluate myocyte contraction. Differentiation steps were assessed by (i) phall…

Functional roles of the sweet taste receptor in oral and extraoral tissues

International audience; Purpose of review: This review summarizes and discusses the current knowledge about the physiological roles of the sweet taste receptor in oral and extraoral tissues. Recent findings: The expression of a functional sweet taste receptor has been reported in numerous extragustatory tissues, including the gut, pancreas, bladder, brain and, more recently, bone and adipose tissues. In the gut, this receptor has been suggested to be involved in luminal glucose sensing, the release of some satiety hormones, the expression of glucose transporters, and the maintenance of glucose homeostasis. More recently, the sweet taste receptor was proposed to regulate adipogenesis and bon…

Odorant metabolizing enzymes in the peripheral olfactory process

Odorant metabolizing enzymes in the peripheral olfactory process

C-terminal amino acids are essential for human heat shock protein 70 dimerization

The human inducible heat shock protein 70 (hHsp70), which is involved in several major pathologies, including neurodegenerative disorders and cancer, is a key molecular chaperone and contributes to the proper protein folding and maintenance of a large number of protein structures. Despite its role in disease, the current structural knowledge of hHsp70 is almost exclusively based on its Escherichia coli homolog, DnaK, even though these two proteins only share ~50 % amino acid identity. For the first time, we describe a complete heterologous production and purification strategy that allowed us to obtain a large amount of soluble, full-length, and non-tagged hHsp70. The protein displayed both …

Recombinant expression of the N-terminal domain of human T1R2 taste receptor: interaction with brazzein, a sweet-tasting protein

The Relationship Between Salivary Redox, Diet, and Food Flavor Perception.

The mouth is the gateway for entrance of food and microorganisms into the organism. The oral cavity is bathed by saliva, which is thus the first fluid that food and microorganisms will face after their entrance. As a result, saliva plays different functions, including lubrication, predigestion, protection, detoxification, and even transport of taste compounds to chemoreceptors located in the taste buds. To ensure its function of protection, saliva contains reactive harmful compounds such as reactive oxygen species that are controlled and neutralized by the antioxidant activity of saliva. Several antioxidant molecules control the production of molecules such as reactive oxygen compounds, neu…

A self-inducible heterologous protein expression system in Escherichia coli

AbstractEscherichia coli is an important experimental, medical and industrial cell factory for recombinant protein production. The inducible lac promoter is one of the most commonly used promoters for heterologous protein expression in E. coli. Isopropyl-β-D-thiogalactoside (IPTG) is currently the most efficient molecular inducer for regulating this promoter’s transcriptional activity. However, limitations have been observed in large-scale and microplate production, including toxicity, cost and culture monitoring. Here, we report the novel SILEX (Self-InducibLe Expression) system, which is a convenient, cost-effective alternative that does not require cell density monitoring or IPTG inducti…

Système d’expression auto-inductible n° 3.026.109

En cours d'enregistrement international N° et date de dépôt : FR1459019 - 2014-09-24 ; n° et date de publication de la demande : FR3026109 - 2016-03-25 (BOPI 2016-12).

Odorant metabolism in olfactory mucus: characterization and impact on olfactory perception

Activités oxydo-réductrices dans la salive : modulation par l’alimentation et importance pour la perception sensorielle des aliments

Resume La salive est un fluide complexe contenant des electrolytes, des molecules organiques, des microorganismes, des debris alimentaires et cellulaires, mais aussi des proteines de differentes natures qui lui permettent d’assurer de nombreuses fonctions. La salive a entre autres un role dans le controle et la modulation des dommages resultant de mecanismes oxydants en bouche. Cet article introduit les principaux composes salivaires impliques dans le stress oxydant et ceux impliques dans la neutralisation de ces especes oxydantes, le maintien du potentiel redox et la reparation des dommages issus de l’oxydation des biomolecules en bouche. Il propose un etat des lieux des connaissances sur …

New insights in vertebrate >

International audience

Investigation of a new chemosensory method using three taste inhibitors to study the taste perception mechanism in domestic cats: examples of bitter, umami and kokumi tastes

Investigation of a new chemosensory method using three taste inhibitors to study the taste perception mechanism in domestic cats: examples of bitter, umami and kokumi tastes. 39. annual meeting - association for chemoreception sciences (AChemS)

Oral and extra-oral receptors: what roles?

La perception du goût est médiée par différents types de récepteurs impliqués dans la perception de chacune des cinq saveurs fondamentales à savoir le salé, le sucré, l’acide, l’amer et l’umami (perception de certains acides aminés tels que le L-glutamate). L’identification de ces différents récepteurs a notamment permis de mieux comprendre les mécanismes moléculaires sous-jacents à ces perceptions. Le nombre de récepteurs pour chacune des saveurs ainsi que l’affinité qu’ils présentent pour les molécules sapides sont directement corrélées à la fonction biologique qui sous-tendent la détection de ces molécules. Ainsi, par exemple les sucres naturels source d’énergie pour l’organisme sont dét…

Impact of Oral Microbiota on Flavor Perception: From Food Processing to In-Mouth Metabolization.

International audience; Flavor perception during food intake is one of the main drivers of food acceptability and consumption. Recent studies have pointed to the oral microbiota as an important factor modulating flavor perception. This review introduces general characteristics of the oral microbiota, factors potentially influencing its composition, as well as known relationships between oral microbiota and chemosensory perception. We also review diverse evidenced mechanisms enabling the modulation of chemosensory perception by the microbiota. They include modulation of the chemosensory receptors activation by microbial metabolites but also modification of receptors expression. Specific enzy…

Implication des enzymes dans la perception chimio-sensorielle : une piste dans les troubles olfacto-gustatifs induits par des xénobiotiques ?

International audience

Le point sur... Perspectives thérapeutiques des inhibiteurs du goût sucré

Nous percevons le goût sucré à l’aide d’un récepteur unique, appelé T1R2/T1R3. Ce récepteur nous permet de détecter tous les divers composés chimiques que nous percevons comme sucrés. De façon surprenante, des études récentes ont montré qu’il était présent dans de nombreux tissus et organes en dehors de la cavité orale. Parce qu’il joue un rôle dans le contrôle métabolique, ce récepteur représente une cible potentielle et prometteuse pour le traitement de l’obésité et des maladies métaboliques, telles que le diabète et l’obésité via notamment l’utilisation d’inhibiteurs spécifiques.

Resolution of the X-ray structure of gurmarin: new insights into the molecular mechanism of sweet taste receptor inhibition

International audience

The implication of OBP28a in Drosophila melanogaster chemosensory perception

National audience; Chemoperception is critical for animals to detect nutritive food and avoid toxic compounds. As many other insects, Drosophila melanogaster uses various semiochemicals including pheromones and food volatiles to identify a suitable ecological niche and a mating partner. Chemosensory detection is mostly mediated by olfactory and gustatory systems involving several multigene chemoreceptor families. Volatile and non-volatile chemicals compounds entering into the sensory organ (sensillum) must be solubilized before being transported through the hydrophilic sensillum lymph bathing the chemosensory neurons. Such perireceptor events involve a family of soluble proteins named odora…

Expression and characterization of the human sweet taste receptor expressed in a mammalian inducible cell line

International audience; Sweet taste perception is mediated by a heterodimeric receptor composed of the two distinct protein subunits, TAS1R2 and TAS1R3. TAS1R2 and TAS1R3 subunits are members of the small family of class C GPCRs. Class C GPCRs share a large N-terminal domain (NTD) linked to the heptahelical transmembrane domain by a cysteine-rich region. TAS1R2/TAS1R3 is the primary receptor for a diverse range of sweet compounds including natural sugars, sweet amino acids, artificial sweeteners and plant sweet-tasting proteins. In order to understand the molecular mechanisms that govern receptor – ligand interactions and the relative contribution of the two subunits to the detection of swe…

Nanofitins targeting heat shock protein 110: an innovative immunotherapeutic modality in cancer.

The presence of an inactivating heat shock protein 110 (HSP110) mutation in colorectal cancers has been correlated with an excellent prognosis and with the ability of HSP110 to favor the formation of tolerogenic (M2-like) macrophages. These clinical and experimental results suggest a potentially powerful new strategy against colorectal cancer: the inhibition of HSP110. In this work, as an alternative to neutralizing antibodies, Nanofitins (scaffold ~7 kDa proteins) targeting HSP110 were isolated from the screening of a synthetic Nanofitin library, and their capacity to bind (immunoprecipitation, biolayer interferometry) and to inhibit HSP110 was analyzed in vitro and in vivo. Three Nanofiti…

Biophysical and functional characterization of the human olfactory receptor OR1A1 expressed in a mammalian inducible cell line

International audience; Olfactory receptors (ORs) play a crucial role in detecting the odorant molecules present in the surrounding environment. These receptors, which belong to class A G-protein-coupled receptors, constitute the largest transmembrane protein family in the human genome. Functional studies showed that the OR family includes members that are able to respond to a large set of odorants and members that are activated by a relatively small number of related odorants. To understand the molecular mechanisms that govern the receptor-ligand interactions, we overexpressed the human OR hOR1A1 in a stable tetracycline-inducible HEK293S cell line. This receptor was engineered by insertin…

New insights in vertebrate 'biotransfolfaction'

International audience

Métabolisme des molécules amères : quel lien avec la perception gustative et l'information toxicologique ?

SILEX : une publication et un brevet pour une équipe du CSGA

C'est un projet mené par Loïc Briand et Fabrice Neiers (équipe de L. Briand), du CSGA. L'équipe a breveté en 2016 une technologie qui permet de transférer la capacité d’induire la production d’une protéine recombinante d’intérêt de manière autonome dans la bactérie Escherichia. coli, sans utilisation d’un milieu de culture particulier. Cette capacité est nommée auto-induction programmée (Self Inductible EXpression system, d’où SILEX.)Les protéines recombinantes représentent une ressource importante car la demande explose dans tous les secteurs industriels : production de médicaments, réalisation de diagnostics médicaux, chimie, agroalimentaire.Afin de produire ces protéines recombinantes, u…

Strategy for recombinant expression of soluble functional N-terminal domain of human sweet taste receptor produced in Escherichia coli

International audience

Characterization of the ligands for the human umami taste receptor

National audience; Among our basics senses, taste and our gustatory system allow us to perceive and recognize essential chemical nutrients present in food. Human can detect and discriminate five basics taste (sweet, bitter, sour, salty and umami) and recent studies proposed a sixth taste for fat. The umami taste is described as a « savory » sensation elicited mainly by L-amino acids and is thought to serve as an indicator of protein rich foods and promote feeding.The umami taste receptor is a heterodimeric receptor composed of the T1R1 and T1R3 subunits. These subunits belong to the family class C G protein-coupled receptors (GPCRs) and are constituted by a large N-terminal domain (NTD) lin…

Implication de l’OBP19b dans la perception gustative des acides aminés chez Drosophila melanogaster

National audience; La chimioperception est nécessaire à la détection des aliments nutritifs et à l’identification des composés toxiques, d’une niche écologique appropriée et des partenaires sexuels. Comme beaucoup d'autres insectes, la mouche du vinaigre, Drosophila melanogaster, possède des capacités chimiosensorielles performantes, la rendant très sensible en lui permettant de détecter et discriminer un large panel de substances chimiques. Chez la Drosophile, cette détection est réalisée par les systèmes chimiosensoriels gustatifs et olfactifs impliquant plusieurs familles de récepteurs. Les composés chimiques volatils et non volatils qui pénétrent les organes sensoriels (sensilles) doive…

Expression and differential localization of xenobiotic transporters in the rat olfactory neuro-epithelium.

International audience; Transporters, such as multidrug resistance P-glycoproteins (MDR), multidrug resistance-related proteins (MRP) and organic anion transporters (OATs), are involved in xenobiotic metabolism, particularly the cellular uptake or efflux of xenobiotics (and endobiotics) or their metabolites. The olfactory epithelium is exposed to both inhaled xenobiotics and those coming from systemic circulation. This tissue has been described as a pathway for xenobiotics to the brain via olfactory perineural space. Thereby, olfactory transporters and xenobiotic metabolizing enzymes, dedicated to the inactivation and the elimination of xenobiotics, have been involved in the toxicological p…

The Crystal Structure of Gurmarin, a Sweet Taste–Suppressing Protein: Identification of the Amino Acid Residues Essential for Inhibition

International audience; Gurmarin is a highly specific sweet-taste suppressing protein in rodents that is isolated from the Indian plant Gymnemasylvestre. Gurmarin consists of 35 amino acid residues containing three intramolecular disulfide bridges that form a cystine knot. Here, we report the crystal structure of gurmarin at a 1.45 Å resolution and compare it with previously reported NMR solution structures. The atomic structure at this resolution allowed us to identify a very flexible region consisting of hydrophobic residues. Some of these amino acid residues had been identified as a putative binding site for the rat sweet taste receptor in a previous study. By combining alanine-scanning …

OBP19b is involved in the taste perception of amino acid in Drosophila melanogaster

Chemoperception plays a crucial role in the detection of nutritive food and avoidance of toxic compounds. It also allows animals to identify a suitable ecological niche and mating partners. As many other insects, Drosophila melanogaster possess a very sensitive chemosensory ability to detect and discriminate a wide panel of semiochemicals. Chemosensory detection is mostly mediated by olfactory and gustatory systems involving several multigene chemoreceptor families. Volatile and non-volatile chemicals compounds entering the sensory organ (sensillum) must be solubilized before being transported through the hydrophilic sensillum lymph bathing chemosensory receptors. Such “perireceptor events”…

Purification, biophysical characterization and first crystallization trials of the ligand-binding domain of the human T1R3 sweet taste receptor

International audience

Effects of oenological tannins on aroma release and perception of oxidized and non-oxidized red wine: A dynamic real-time in-vivo study coupling sensory evaluation and analytical chemistry.

International audience; Addition of oenological tannins claims to have a positive impact on wine stability, protection from oxidation and likely sensory persistence. However, their role on red wine aroma during oxidation is controversial. The present study aims at investigating the effect of addition of oenological tannins on wine flavour (mainly aroma) before and after air exposure. Temporal Dominance of Sensations, a dynamic sensory evaluation, was coupled with a dynamic chemical measurement (nosespace analysis) using a Proton-Transfer-Reaction Mass-Spectrometer connected to the nasal cavity of 17 assessors. Results showed that the oxidation of a non-oaked Pinot Noir red wine decreases th…

Enzymatic modulation of the bitter taste in Human and Drosophila

Enzymatic modulation of the bitter taste in Human and Drosophila. 4. International Conference on Agricultural and Biological Sciences (ABS 2018)

ARET : colloque 2018 au CSGA Dijon. 28 et 29 mai 2018 - CSGA, 9E boulevard Jeanne d'Arc, Dijon

L'Association pour la REcherche en Toxicologie (ARET) organise un colloque sur le thème "Substances odorantes et sapides : du plaisir des sens aux cibles biologiques", lundi 28 et mardi 29 mai 2018 au CSGA. Ce colloque bénéficie du soutien du département AlimH. Invité d'honneur de la table ronde: Roland Salesse.

Drosophila melanogaster glutathione transferase overexpressed in the sensory organs after exposure to bitter molecules in food

International audience

Functional characterization of the ligand binding domain of the cat T1R1 taste receptor

The umami taste receptor is a heterodimeric G-protein coupled receptor (GPCR), composed of two subunits called T1R1 and T1R3. Both subunits are class C GPCRs whose members share a common architecture composed of a large N-terminal domain (NTD) connected to a heptahelical transmembrane domain by a short cysteine-rich domain. Cellular assays combined with molecular docking and site-directed mutagenesis studies have revealed that the NTD of the T1R1 subunit contains the primary binding site for umami stimuli, such as L-glutamate (L-Glu) for humans. Inosine-5’-monophosphate (IMP) binds close to the opening of the NTD, responsible for the characteristic umami synergy between L-Glu and IMP. Funct…

Les inhibiteurs du goût sucré : perspectives thérapeutiques

This review summarizes and discusses the current knowledge concerning the physiological role of the sweet taste receptor (T1R2/T1R3) and the potential therapeutic perspectives concerning its inhibition. The functional expression of the sweet taste receptor has also been described in many extra-oral tissues where it has been proposed that the receptor participated in the regulation of metabolic processes. The receptor has been highlighted in various organs such as the intestine, pancreas, bladder, brain, and more recently in the bone and adipose tissue. In the intestine, T1R2/T1R3 receptor has been shown to be involved in the detection of luminal glucose, cytokine release of certain hormones…

Odorant-binding protein engineering: impact on binding properties

OBP19b is involved in the taste perception of amino acid in Drosophila melanogaster

International audience

P45 - Drosophila melanogaster glutathione transferase overexpressed in the sensory organs after exposure to bitter molecules in food

International audience

Optimized vector for functional expression of the human bitter taste receptor TAS2R14 in HEK293 cells

International audience

Structure-function relationships of brazzein, a sweet-tasting protein and its interactions with the human sweet taste receptor

International audience; Brazzein is a small heat- and pH-stable sweet-tasting protein isolated from the West African plant, Pentadiplandra brazzeana. Brazzein combines a highly sweet potency, a long history of human consumption, and a remarkable stability, giving it great potential as a natural sweetener. Due to the difficulties of obtaining brazzein from its natural source, several efforts have been made to express brazzein using various heterologous expression systems. Brazzein like all classes of sweet compounds (natural sugars, natural and artificial sweeteners) are perceived through the activation of the T1R2/T1R3 heterodimeric sweet taste receptor. T1R2 and T1R3 subunits are members o…

Structural behaviour differences in low methoxy pectin solutions in the presence of divalent cations (Ca 2+ and Zn 2+ ): a process driven by the binding mechanism of the cation with the galacturonate unit

International audience; In this paper, we compare the interactions between low methoxy pectin (LMP) and either Ca2+ or Zn2+ in semi-dilute solutions. Intrinsic viscosity and turbidity measurements reveal that pectin-calcium solutions are more viscous, but yet less turbid, than pectin-zinc ones. To get a molecular understanding on the origin of this rather unexpected behavior, we further performed isothermal titration calorimetry, small angle neutron scattering experiments, as well as molecular dynamics simulations. Our results suggest that calcium cations induce the formation of a more homogeneous network of pectin than zinc cations do. The molecular dynamics simulations indicate that this …

Interaction of the n-terminal domain of human t1r2 taste receptor with brazzein, a sweet-tasting protein

Brazzein is a small (6.5 kDa) sweet-tasting protein originating from the fruit of Pentadiplandra brazzeana, a plant found in West Africa. Brazzein like all classes of sweet compounds is perceived through the activation of the T1R2/T1R3 heterodimeric sweet-taste receptor. T1R2 and T1R3 subunits are members of the small family of class C G-protein coupled receptors (GPCRs). Class C GPCRs possess a large N-terminal domain (NTD) linked to seven transmembrane domain by a cysteine rich domain (CRD). The NTD of T1R2 (T1R2-NTD) has been shown to contain the primary binding site for most of the sweet ligands. However, brazzein has been shown to require CRD of human T1R3 for receptor activation [1]. …

MIRACULINE as a natural sweetener; the N3S QUALIMENT project. Potential interest in baking

Miraculine is a glycol-protein extracted from the Miracle fruit which is a berry(Synsepalum dulcificum - Sapotaceae family, Daniell-1952). Common names for the miracle fruit are miracle berry, miraculous berry, sweet berry …. It originated from West Africa and is grown under tropical climate. In the 1970s, it has been attempted to commercialize miraculin on a large scale in the United States under the name of Miralin. The FDA allowed and then blocked the development of this new natural sweetener because no non-toxicity test had been performed. At the same time, aspartame was authorized. Today, miraculin is still not permitted in the USA and in Europe (classified as Novel Food). Besides, it …

Structural and enzymatic characterization of a Drosophila melanogaster glutathione transferase overexpressed in the sensory organs after exposure to bitter molecules in food

Glutathione transferases (GSTs) are ubiquitous key detoxification enzymes that catalyze the conjugation of glutathione to a large variety of xenobiotic chemical including odorants and sapid molecules. A previous study in Drosophila melanogaster demonstrated the existence of a GST specifically expressed in the antenna and involved in signal termination by catalyzing biotransformation of odorant molecules. Genomic analysis allows identifying forty GSTs in Drosophila melanogaster but their biochemistry is poorly documented. Here we demonstrated that among the GSTs, dmelGSTD2-2 was strongly and preferentially overexpressed in the sensory organs (antennae, proboscis, legs, wings) after an exposu…

Myoglobin on Silica: A Case Study of the Impact of Adsorption on Protein Structure and Dynamics

International audience; If protein structure and function changes upon adsorption are well documented, modification of adsorbed protein dynamics remains a blind spot, despite its importance in biological processes. The adsorption of metmyoglobin on a silica surface was studied by isotherm measurements, microcalorimetry, circular dichroïsm, and UV-visible spectroscopy to determine the thermodynamic parameters of protein adsorption and consequent structure modifications. The mean square displacement and the vibrational densities of states of the adsorbed protein were measured by elastic and inelastic neutron scattering experiments. A decrease of protein flexibility and depletion in low freque…

Taste Bud Density and Composition of Saliva in Patients Suffering from Taste Disorders Compared to Healthy Individuals

Aim: Previous studies have shown a correlation between fungiform papillae density and acuity of taste. In addition changes of salivary composition in oral sensation complaints were observed as well. Aim of this prospective investigation was to determine correlations between the fungiform papillae density, salivary composition and taste acuity of healthy individuals and patients with idiopathic taste disorders.Material & Methods: The present study was performed in 81 patients with a mean age of 58±13 years complaining of gustatory dysfunctions and groups of 20 younger (age 24±3 years) and 20 older healthy subjects (age 55±10 years).Taste perception was measured using taste strips and electro…

Collisional mechanism of ligand release by Bombyx mori JHBP, a member of the TULIP / Takeout family of lipid transporters.

International audience; Juvenile hormones (JHs) regulate important processes in insects, such as postembryonic development and reproduction. In the hemolymph of Lepidoptera, these lipophilic sesquiterpenic hormones are transported from their site of synthesis to target tissues by high affinity carriers, the juvenile hormone binding proteins (JHBPs). Lepidopteran JHBPs belong to a recently uncovered, yet very ancient family of proteins sharing a common lipid fold (TULIP domain) and involved in shuttling various lipid ligands. One important, but poorly understood aspect of JHs action, is the mechanism of hormone transfer to or through the plasma membranes of target cells. Since many membrane-…

Curvature and Torsion of Protein Main Chain as Local Order Parameters of Protein Unfolding

International audience; Thermal protein unfolding resembles a global (two-state) phase transition. At the local scale, protein unfolding is, however, heterogeneous and probe dependent. Here, we consider local order parameters defined by the local curvature and torsion of the protein main chain. Because chemical shift (CS) measured by NMR spectroscopy is extremely sensitive to the local atomic environment, CS has served as a local probe of thermal unfolding of proteins by varying the position of the atomic isotope along the amino-acid sequence. The variation of the CS of each C(alpha) atom along the sequence as a function of the temperature defines a local heat-induced denaturation curve. We…

Characterization of Drosophila Delta glutathione transferases involved in isothiocyanate detoxification and perception

International audience

The X-ray structure of gurmarin provide new insights into amino acid residues essential for inhibition of the rat sweet taste receptor

International audience; Gurmarin is a polypeptide isolated from the Indian plant Gymnema sylvestre, which specifically suppresses sweet taste in rodents without affecting responses to other basic taste stimuli, such as HCl, NaCl, and quinine. Although the exact mechanism of gurmarin inhibition is not known, it has been shown that gurmarin acts via the T1R2/T1R3 sweet taste receptor. The gurmarin molecule is made of 35 amino-acid residues and three intramolecular disulfide bridges. We report herein the 1.45 Å X-ray structure of gurmarin heterologously produced using the yeast Pichia pastoris. The structure revealed a typical knottin fold, which is compared with previously reported NMR soluti…

Interactions between odorants and glutathione transferases in the human olfactory cleft

AbstractXenobiotic metabolizing enzymes and other proteins, including odorant-binding proteins located in the nasal epithelium and mucus, participate in a series of processes modulating the concentration of odorants in the environment of olfactory receptors (ORs) and finely impact odor perception. These enzymes and transporters are thought to participate in odorant degradation or transport. Odorant biotransformation results in 1) changes in the odorant quantity up to their clearance and the termination of signaling and 2) the formation of new odorant stimuli (metabolites). Enzymes, such as cytochrome P450 and glutathione transferases (GSTs), have been proposed to participate in odorant clea…